President Trump's signature campaign issue was his promise to build a wall along the U.S.-Mexican border and make Mexico pay for it. Having shown new flexibility on both the border wall and amnesty for illegal immigrants, he may have fenced himself in on immigration.

But will he pay for it?

It's a question that has been on the mind of Trump's supporters and detractors ever since jubilant Democratic leaders emerged from a dinner meeting with the president claiming a breakthrough on the Deferred Action for Childhood Arrivals program. The program was created by former President Obama's legally questionable executive order to shield children of illegal immigrants from deportation. Trump announced he was rescinding the order in six months, giving Congress time to address the question and resolve it with legislation.

"We had a very productive meeting at the White House with the president," Senate Minority Leader Chuck Schumer, D-N.Y., and House Minority Leader Nancy Pelosi, D-Calif., said in a joint statement. "The discussion focused on DACA. We agreed to enshrine the protections of DACA into law quickly, and to work out a package of border security, excluding the wall, that's acceptable to both sides."

White House press secretary Sarah Sanders immediately pushed back. "While DACA and border security were both discussed, excluding the wall was certainly not agreed to," she said, adding that the Democrats' characterization of the meeting was oversimplified, if not misleading. The rough contours of an agreement were in place, but there was no deal yet that could serve as actionable legislation.

Yet, Trump's wobbliness about the wall was real. Both sides acknowledged that he did not say he would stop fighting to build the wall. "The president made clear he would continue pushing the wall, just not as part of this agreement," a Schumer spokesman said afterward. "Very important is the wall," Trump said in Florida the following day.

Nevertheless, Trump had already backed down from a threat to force a government shutdown if Congress did not provide money to build the wall. Now, he was signaling that he was willing to consider granting legal status to a group of illegal immigrants even without certainty that the wall would be built. "DACA now and the wall very soon, but the wall will happen," the president insisted to reporters.

Trump even seemed to be changing the definition of the wall. "The WALL, which is already under construction in the form of new renovation of old and existing fences and walls, will continue to be built," he tweeted.

"I distinctly remember the crowds chanting 'Renovate Existing Fences!' 'Renovate Existing Fences,'" shot back a popular conservative Twitter user.

Supporters feel stung

Democrats and Never Trump-conservatives have highlighted the president's putative deal for "dreamers" as evidence that he is a con man who has sold out his base. Some even suggested it was the latest humiliation of Attorney General Jeff Sessions, the administration's leading immigration hawk, who was sent out to announce Trump's shift of policy.

A subset of Trump's most fervent supporters agree, and they are furious. Conservative columnist Ann Coulter, author of the election-year book In Trump We Trust, has taken to tweeting daily wall construction updates. "Miles completed yesterday — zero," she writes. "Miles completed since Inauguration — zero."

"A re-elect in 2020 would be very difficult for the president if amnesty goes with DACA and if a wall is not at least under robust construction by then," Rep. Steve King, R-Iowa, complained to CNN.

Rep. Louie Gohmert, R-Texas, told Fox News, "When I've spent so many nights there on the border, the border patrol makes clear — I've seen it with my own eyes — when somebody in Washington says, ‘let's talk about legalizing anybody,' then there is a surge.

"We have got to secure the border, and I refuse to talk about legalizing anybody until that border is secure. We have got to have a wall, and we've got to secure it. And once that is done, we'll talk about that."

Breitbart, the pro-Trump conservative news site that has recently been reunited with its past chairman, former White House chief strategist Steve Bannon, has taken to calling the president "Amnesty Don."

Democrats may believe the president's back is to the wall, but Trump thinks it is the other way around. Just as when he threatened to let Obamacare "collapse" to force recalcitrant lawmakers to the bargaining table, he has set in motion a policy outcome, exposing a sympathetic group of undocumented immigrants to heightened risk of deportation, that no one wants, least of all Democrats. To avoid that outcome, they will have to make a deal.

Some immigration hawks are skeptical, and in support of their skepticism they point to Trump's own tweet, in which he said he might revisit the issue if Congress fails to act on DACA within his six-month deadline. "All he had to do was let the lawsuit go forward," a Republican congressional aide told the Washington Examiner, referring to an anti-DACA suit by conservative attorneys general that ostensibly prompted Trump to make a decision. There was a good chance, they argued, that the constitutionally shaky DACA would have been voided by the courts, putting the ball back in Congress' court without Trump or the Republicans owning the issue.

A deal using DACA

Still, Trump thinks he can get tighter immigration controls in exchange for legalizing "dreamers." He said, "We're working on a deal for DACA, but a lot has to do with the amount of security. We want very heavy security at the border."

So, if not the wall, what?

The wall has become a symbol of Trump's steadfast opposition to lax immigration policy. Because the wall and Trump are linked so strongly, Democrats are determined to oppose it despite their previous agreement to border fencing. The Secure Fence Act of 2006 passed the Senate 80-19 with Schumer and Barack Obama and Hillary Clinton, who were both senators at the time, all voting aye.

Public opinion polls have also suggested Trump's association with the wall has cost it support. Pew Research Center found backing for border fencing held steady at 46 percent nationally from 2007 to 2015, but fell to 36 percent in March 2016. CBS News/New York Times polling showed support falling from 45 percent in January 2016 to 39 percent in July. Rand Corp. surveyed the same individuals and found a 10-point drop in support for a wall between December 2015/January 2016 and July/August 2016.

The Washington Post ran a story about some of these poll results headlined, "Donald Trump is making the border wall less popular." But among Trump's base, the wall is a rallying cry. "Build the wall!" rivaled "Lock her up!" as the top chant at Trump's raucus campaign events, a fact he noticed.

"You know, if it gets a little boring, if I see people starting to sort of, maybe, thinking about leaving, I can sort of tell the audience, I just say, ‘We will build the wall!' and they go nuts," Trump told the New York Times editorial board last year.

Even so, many immigration hawks don't think the wall is the most important priority. "It's clear that Trump has emphasized the wall over everything else," said Jerry Kammer, a Pulitzer Prize-winning reporter and senior fellow at the restrictionist Center for Immigration Studies, who just published a book about the lack of effective worksite enforcement. "He seems not to understand that the power of the jobs magnet is so great that unless it is turned off, many people will continue to find ways to come over, under, or around a wall, or simply to overstay their temporary visas.

"If the worksite remains accessible to unauthorized workers, they will continue to have a powerful incentive to keep on trying," Kammer added, telling the Washington Examiner, "As you know, the key to worksite enforcement and employer sanctions is a credible means of determining whether a worker is authorized. That's why Fr. [Theodore] Hesburgh, way back in 1980, said that without it, worksite enforcement would be ‘like kissing your sister.' " (Hesburgh chaired an immigration-reform commission under President Carter.)

That's why Sen. Tom Cotton, R-Ark., a leading immigration hawk in Congress, isn't focusing on the wall in his preferred DACA deal. He told a Washington dinner organized by Hillsdale College in September that the wall "is mostly a funding issue, not a policy issue." He pointed to the $1.6 billion in wall funding that passed the House, totally separate from any DACA legislation.

"We can, if we choose, grant citizenship to those illegal immigrants who came here through no fault of their own as kids and who've otherwise been law-abiding, productive citizens," Cotton said in his speech to the gathering. "But if we do, it will have the effect of legalizing through chain migration their parents, the very people who created the problem by bringing the kids here illegally."

"A standalone amnesty will not do, nor will an amnesty with vague promises of ‘border security,' which never seem to materialize or get funded once the pressure is off Congress."

Cotton told the Washington Examiner the following day, "If you've got kids, put yourself in the position of a mom or dad in El Salvador, the most dangerous place in the world, the home of MS-13. If the U.S. gives legal status to 20- and 30-somethings who came here as children, what price would you pay to get your child here now?"

Cotton would like to pair DACA legalization with the Reforming American Immigration for a Strong Economy Act, a bill he has introduced with Sen. David Perdue, R-Ga. Over in the House, Rep. Lamar Smith, R-Texas, a veteran of the heated 1990s immigration debates, has introduced companion legislation.

Their bill would create a point system for employment-based immigration, giving advantages to prospective entries who have needed technical skills or are proficient in English, while limiting family-based immigration preferences to the spouses and minor children of American citizens and legal permanent residents. It would also eliminate the diversity visa lobby.

All this would have the cumulative effect of cutting legal immigration in half over 10 years, which has made the bill a nonstarter in the Senate. There, members from both parties are in favor of increasing immigration levels, as well as legalizing most of the illegal immigrants already in the United States, for over a decade.

But Trump has raised the profile of immigration hawks in the Republican Party, and the RAISE Act's provisions limiting chain migration are highly relevant to the DACA debate. Chain migration is the process by which each group of immigrants gains citizenship or permanent legal residency and then sponsors relatives for future immigration.

"If we don't change underlying laws about chain migration, which account for almost two-thirds of all green cards this country gives out every year," Cotton warned the Washington Examiner, "then this could be the largest amnesty in the history of the United States."

Trump endorsed the RAISE Act at the White House in August, with Cotton and Perdue at his side. "CHAIN MIGRATION cannot be allowed to be part of any legislation on Immigration!" the president tweeted after his DACA dinner with Democrats.

The president continues to say he is against amnesty, despite telling the Washington Examiner this year, "Well, I always understood that with DACA, we need special heart." He has described DACA as one of Obama's "two unconstitutional amnesties" in an immigration speech during the campaign that was reportedly written by Bannon and White House adviser Stephen Miller.

"We're not talking about that," Trump insisted this month. "We're not talking about amnesty at all." Most immigration hawks would define legal status for DACA recipients as amnesty, however, and it's a deal many of them would take if merged with proposals such as Cotton's.

"Solution is to write a bill that simply puts the childhood arrivals back to where they were under DACA but does so permanently," former Rep. Tom Tancredo, R-Colo., told the Washington Examiner. "Work permits, no threat of deportation if they keep their noses clean, and no path to citizenship. That's what Obama granted them only, as he said, it was temporary."

Cotton does support a path to citizenship for those protected by DACA, but otherwise agrees with the former chairman of the hardline Congressional Immigration Reform Caucus. "Of course, I would attach mandated E-Verify because it would solve about 85 percent of the problem," Tancredo said, refering to a system employers can use to verify employees' immigration status. "You haven't heard that proposed because if, by some weird fluke it passed, the immigration problem would solve itself. The Chamber of Commerce, the Koch brothers and the open border lobby would never stand for that."

But would the Democrats?

Getting Democrats on board

Right now, Trump's immigration negotiating partners from across the aisle are mostly pushing the 2017 Dream Act, which critics note would legalize a larger number of illegal immigrants than is currently protected by DACA. "It grants amnesty to over 3 to 5 million people, not ‘childhood arrivals,'" Tancredo said. "Unfortunately, both media and Republican opponents have been too lazy to read the bill."

Democrats have in the past been willing to include more funding for border security in immigration reform legislation. But they have balked at strong E-Verify provisions, which are used to flag the hiring of illegal immigrants and prevent document fraud, as have some Republicans who find them too onerous for employers and potentially injurious to civil liberties. In past immigration negotiations, such as the Gang of Eight deal, immigration hawks did not have a place at the table.

Now, in theory, there is an immigration hawk at the head of the table. Trump has an opportunity to boost congressional efforts that would have been ignored or suppressed by other recent Republican presidents. More restrictionist conservatives are willing to seize the opportunity.

"[Cotton's] focus right now is on getting the RAISE Act included in the final deal," said his communications director Caroline Rabbit. "Sen. Cotton and Sen. Perdue have been working to educate all of their colleagues, including Democrats, on the RAISE Act and will continue with those efforts." But they sound willing to negotiate the details as long as DACA is combined with some effort to reduce incentives for illegal immigration.

Trump faces two challenges. First, selling Democrats and many Republicans, including some in the congressional leadership, on making concessions to immigration hawks. Second, persuading his base to accept any compromise, even if it includes those concessions to hardline restrictionists.

Fixing DACA with legislation is broadly popular, but those who oppose it disproportionately back Trump. A HuffPost/YouGov poll found that only 39 percent of Trump voters want DACA beneficiaries to stay in the country. DACA foes had greater intensity, with 3 in 10 strongly opposing the program compared to just a little more 1 in 10 strongly supporting it. Moreover, those who "strongly approve" of Trump's presidential job performance are against DACA by a margin of 33 points, according to the survey.

Potentially more significant is the fact that Trump did not get those supporters to chant "End chain migration," "Pass E-Verify," or "Abolish the diversity visa lottery" at his campaign rallies. The battle cry was "Build the wall." Even if those other policies are more likely to address Trump voters' real problems with immigration, the wall is the policy Trump sold them on. Whatever its effectiveness in actually preventing illegal immigration, it is the concrete symbol of the policies a great many Trump supporters want, and failing to build it in concrete and steel could be profoundly disappointing to the president's erstwhile supporters. See, again, Coulter's twitter feed.

Democratic resistance to the wall is strong, which is why it has been left out of must-pass legislation such as hurricane relief bills or even DACA. Some Republicans, especially in border states, have been surprisingly antagonistic too. Rep. Will Hurd, R-Texas, called it a "third century solution" in an op-ed. Austin Petersen, a GOP Senate candidate in Missouri, described the wall to the Washington Examiner as a "New Deal-style public works project that raises spending and steals Republican voters' land."

Trump appears to understand that the wall is more relevant to the spending fights than DACA legislation. "[T]hey cannot obstruct for a wall because we definitely need a wall," he said of congressional Democrats. But that sets wall boosters up for disappointment whenever funding for the project cannot get through the Senate.

The president could wind up agreeing to the Democrats' terms on DACA without having laid a brick along the souther border. But even if he delivers what congressional immigration hawks want, it's possible some of his voters will feel a letdown. An immigration deal that is tougher on enforcement than the Gang of Eight was, while legalizing a much smaller number of illegal immigrants, could be a bigger win for enforcement advocates than ever appeared possible under the Bush or Obama administrations. But it might still be seen as a loss by those wishing for the wall.

Regardless of whether Trump builds the wall, he has certainly built up expectations.

"While it's difficult to be optimistic that Congress and the executive branch would be willing to take on the cheap labor lobby, the power of the populist backlash that led to the election of Trump may be so great that Congress will be willing to end the hypocrisy and get serious at the worksite," Kammer said. "Until now, throwing money at the Border Patrol has been its default option for demonstrating a phony determination to stop illegal immigration."

Immigration hawks are left hoping the president behind The Art of the Deal can get them a better deal.