Questions abound as lawmakers return to Washington from their August recess with a full plate of must-pass bills and numerous campaign promises that remain to be fulfilled. But the most pressing may be: Can the marriage between President Trump and congressional Republicans be saved?

Voters arranged a shotgun wedding between them by giving them control of both ends of Pennsylvania Avenue. But unified government has proven to be anything but united. The White House and its putative Capitol Hill allies have pointed fingers at each other over their stalled agenda. The honeymoon, if there ever was one, is over.

Trump drove the point home in his speech in Springfield, Mo. launching his tax reform agenda. He attacked the state's vulnerable Democratic senator, saying, "We must, we have no choice, we must lower our taxes. And your senator, Claire McCaskill, she must do this for you. And if she doesn't do it for you, you have to vote her out of office."

The remark raised eyebrows among some ethics watchdogs, even though Trump isn't covered by the Hatch Act prohibiting campaign activity by government workers on the clock (his speechwriters and other White House staffers are), but Republicans loved it. "It's much better than when he is attacking John McCain, Dean Heller, or Jeff Flake," said a GOP congressional aide. Yet, it didn't take long for Trump to take a shot at the Republican majority, too, saying, "I don't want to be disappointed by Congress, do you understand me?"

While he has regularly slammed Democrats as "obstructionists," he hasn't shied away from saying congressional Republicans have let him down before. He's blamed Senate Majority Leader Mitch McConnell, R-Ky., and McCain, R-Ariz., for the failure of Obamacare repeal. He's said McConnell and House Speaker Paul Ryan, R-Wis., have made a "mess" by ignoring his advice on the debt ceiling.

McConnell in particular has been open about the limitations of trying to lead a 52-48 Republican Senate that still allows filibusters for many important pieces of legislation. Speaking to a Kentucky Farm Bureau breakfast, he darkly compared his position to to that of a groundskeeper at a cemetery. "Everybody's under you, but nobody's listening," McConnell quipped, a joke reminiscent of Bob Dole's 1980s description of himself as the "majority pleader."

President Trump hasnt shied away from saying congressional Republicans have let him down before. Hes said Senate Majority Leader Mitch McConnell, R-Ky., and House Speaker Paul Ryan, R-Wis., have made a mess by ignoring his advice on the debt ceiling. (AP Photos)

Trump has also shown no hesitation piling on new items to the crowded legislative to-do list. He has threatened a government shutdown if Congress fails to fund the border wall, implying he would veto a spending bill passed by Republican lawmakers if they did not comply with his wishes. Democrats and a surprising number of border-state Republicans are balking at this request.

Most previous high-profile government shutdowns have occurred when Congress and the White House are controlled by two different parties. Republicans have generally taken the political hit for them in the past, even when Democrats were involved. In this situation, there would be no one else to blame.

"Here, we have a guy who's barely a Republican lecturing real Republicans on how to pass legislation," said a second GOP Hill staffer. "It drives me crazy."

It's a common complaint among Republican sources. So are arguments that Trump didn't do enough to prevent the legislative setbacks he now bemoans. They say the Russia probe, the West Wing chaos, Charlottesville, and low approval ratings are jeopardizing the congressional majorities, and that intraparty bad blood will only get worse if the Republican agenda doesn't start moving soon.

"The president's loyalty has always been to the voters who put him in the White House," said Mark Serrano, a Republican strategist who serves on the advisory board of Trump's reelection campaign. "The conflict we see between establishment politicians, including Republicans, and the president is to be expected.

"A lot of change was sought by the voters in 2016," he continued. "They rejected the party establishment of both parties. They rejected the media."

Trump has also shown no hesitation piling on new items to the crowded legislative to-do list. He has threatened a government shutdown if Congress fails to fund the border wall.

Some Trump supporters are even blunter. "President Trump is fighting for the millions of Americans who are tired of the excuses and are demanding results," said Erin Montgomery, communications director for America First Action, a pro-Trump super PAC. "So, whether you're Democrat or Republican, either embrace the moment and join the movement, or get the hell out of the way."

Nevertheless, there remains optimism that the fall will be different. "Maybe it takes an act of God to get an act of Congress," a White House aide said. That has arrived in the form of Hurricane Harvey, a devastating storm in which parts of Texas and Louisiana, both states Trump carried, bore the brunt. Republicans have every incentive to cobble together a disaster relief package.

Texan John Cornyn is the second-ranking Republican in the Senate. His junior senator is Ted Cruz, the kind of influential conservative lawmaker who could normally be counted on to rail against extraneous spending in federal relief bills. Trump has said publicly that he wants the response to Harvey to be a model for how the government should deal with future natural disasters. Some Republicans are hopeful this will also get him to buckle on a border wall shutdown.

"We want to be looked at five years, 10 years from now, as this is the way to do it," the president said in Corpus Christi last month, describing the recovery effort as "very effective." But he acknowledged, "We'll congratulate each other when it's all finished."

"On a couple of items, they are going to have to deliver and they know it," said Ford O'Connell, a Republican strategist. "Debt ceiling, hurricane relief funding." The border wall will be tougher. "You don't want a shutdown with Harvey," he added.

Clock ticking on debt ceiling

[M]y strong preference is that we have a clean debt ceiling, but the most important issue is the debt ceiling will be raised in September, Treasury Secretary Steven Mnuchin said.

Unlike many other items in the legislative calendar, the debt ceiling comes with a hard deadline. Congress has until Sept. 29 to extend the debt ceiling. In 2011, waiting until the last minute to do that hurt Washington's credit rating and caused stocks to drop. President Barack Obama compared conservative Republican holdouts to "hostage takers."

The Trump administration has signaled its support for a "clean" debt ceiling increase, which means an increase that's not tied to any other legislation. "Yes" was White House press secretary Sarah Sanders' one-word response when asked at a daily briefing if that was the president's desire.

"[M]y strong preference is that we have a clean debt ceiling, but the most important issue is the debt ceiling will be raised in September," Treasury Secretary Steven Mnuchin told reporters, adding he was "100 percent confident" it would happen and that he, Trump and congressional leaders are all "completely on the same page."

Many Republicans on Capitol Hill would like to hear this from the president himself, however. The feeling is that this would give cover to members who vote for a clean increase over conservative objections, and may even keep some of those would-be conservative defectors in line. At this writing, they haven't heard it. Instead, Trump tweeted that the debt ceiling increase should have been tied to the popular VA reform legislation that already passed Congress and was signed into law.

"Could have been so easy — now a mess!" Trump posted. Administration officials have downplayed the significance of the remark. "What the president said was that his strong preference had been that when they passed the VA bill before they left, that they attach the debt ceiling to that so that we wouldn't be dealing with this in September," Mnuchin explained.

"The government intends to pay its debts, and the debt ceiling will be raised," the treasury secretary added.

"It is important that the Republican leadership begin to create the beginning of a belief that a Republican-controlled Congress can do the things necessary for governing and having a positive impact on people's lives," said Ed Pozzuoli, a GOP strategist.

For all their misgivings about each other, most Republicans feel that they are in this together and will need to have something to show for their majorities when many of them face the voters in the 2018 midterm elections.

"In the end, the American people, I think, are willing to forgive us not getting everything done," Rep. Steve Stivers, R-Ohio, chairman of the National Republican Congressional Campaign Committee, told the Washington Examiner last month. "But they're not willing to accept us getting nothing done."

Tax reform could bring them together

Ryan has described tax reform as the focus literally [of] my adult life and a potential cure for the political anxiety gripping the country.

Republican lawmakers may be bewildered by Trump, frustrated by his constant tweeting, unpredictability and what they see as his inattention to policy details. But most of them have to respect the fact that he is popular with their supporters despite national job approval ratings below 40 percent. Tellingly, all the Republicans interviewed for this article who were especially critical of Trump spoke on the condition of anonymity.

By the same token, as much as Trump is increasingly holding congressional Republicans at arm's length out of frustration with the slow pace of change in Washington and to shield himself from any legislative failures, he so far remains willing to let them fill in the details on issues such as tax reform and healthcare, signing whatever they are able to pass.

Vice President Mike Pence remains a popular figure among mainstream conservatives. Some are still hopeful that the newly installed White House chief of staff, John Kelly, will have some calming effect on West Wing turnover and organization, if not the president himself.

The main reason some of the more reluctant Republicans in Congress supported Trump in the first place, and remain on board in spite of many controversies today, is that they expect him to sign their shared agenda, which languished for eight years under Obama, into law. That expectation remains unchanged, largely because of the president's own words.

"I am sitting in the Oval Office with a pen in hand, waiting for our senators to give it to me," Trump implored during one of the failed attempts to repeal and replace parts of Obamacare. When he spoke about tax reform, he outlined basic principles that would be acceptable to most Republicans in Congress and mostly got out of the way on the specifics.

"That is why the foundation of our job creation agenda is to fundamentally reform our tax code for the first time in more than 30 years," Trump said. "I want to work with Congress, Republicans and Democrats alike, on a plan that is pro-growth, pro-jobs, pro-worker, and pro-American."

Tax reform is the issue that Republicans are most pinning their hopes on after their healthcare stalemate. They are far more united on what to do about tax rates than they were on how to reform Medicaid or restructure the Obamacare exchanges. They believe it is the best thing they can do to stimulate economic growth, create jobs and boost wages. And many of them think that if tax reform passes, it will open the floodgates of successful Republican legislating.

Ryan has described tax reform as the focus "literally [of] my adult life" and a potential cure for the political anxiety gripping the country. House Ways and Means Chairman Kevin Brady, R-Texas, called it an opportunity to "create jobs, grow paychecks, and improve the lives of all Americans." Sen. David Perdue, R-Ga., said "failure to deliver results" on taxes "is not an option."

"Four percent growth a year would be great for jobs, great for the deficit," Pozzuoli said. "We could bring a true competitive advantage back to American companies."

Trump loyalists are similarly bullish. "If we want to build on the progress the president has made with the economy, we have already seen the success with the deregulation," Serrano said. "The next step for growth is tax cuts."

The president made a similar argument himself. "Our self-destructive tax code costs Americans millions and millions of jobs, trillions of dollars, and billions of hours spent on compliance and paperwork," Trump said in Springfield. "And you have seen what's happening with regulations — they're going fast. We need regulations, but many of them are unnecessary, and they're going fast."

What role the president should play in advancing tax reform is the subject of some debate. A lot depends on how individual Republicans feel about his input into healthcare. After an Obamacare reform bill passed the House, members of the whip team came forward and praised Trump's efforts at getting the plan over the finish line.

House Majority Leader Kevin McCarthy, R-Calif., said at the White House event marking the healthcare vote that Trump had given him a list of members to call to win their support for the bill. "And Mr. President, they all voted for the bill," he added. House Majority Whip Steve Scalise, R-La., told the Washington Examiner this year that the president did everything they asked of him.

A steeper climb in the Senate

Trump threatened Sen. Dean Heller, R-Nev., to his face in public. Trump said of Heller, He wants to remain a senator, doesnt he?

The reviews of Trump's lobbying effort in the Senate, where the outcome was different, were much less positive. He threatened Sen. Dean Heller, R-Nev., to his face in public. Trump said of Heller, one of the party's few vulnerable Senate incumbents next year, "He wants to remain a senator, doesn't he?"

Senators are less likely than House members to be awed by phone calls from the president. Many envision themselves being president one day. McCain, the critical vote against "skinny" repeal in the Senate, was the 2008 Republican presidential nominee.

After the healthcare failure, it became more common to hear Republicans say they wanted to work around Trump on tax reform. But a former leadership aide who was otherwise critical of Trump cautioned the Washington Examiner that sweeping changes to the tax code or healthcare system don't pass without some form of presidential leadership.

While some GOP lawmakers would still like to see the president be more hands-off until it comes time to sign a bill, both because of his approval ratings and his contentious relationship with Congress, others have called for him to be as active in winning over the public as President Ronald Reagan was when tax reform was last achieved in 1986. Rep. Sean Duffy, R-Wis., told the Washington Examiner that Trump should be "doing two speeches a week."

"The best thing the president can and will do is rally the support of the American people," said Serrano, adding this could be the model for future successful Republican legislation. "I'd expect to see a lot of Great Lakes states on the schedule." Then who knows what is possible, maybe even a revival of healthcare talks.

That's the optimistic take. Ideally, wonks in Congress write the bills, leadership makes the deals, Trump cheerleads and gins up the enthusiasm of the base, Republicans rack up wins ahead of 2018. On the big-ticket items, however, so far this approach hasn't worked.

Trump also has some legislative agenda items of his own, independent of what congressional leaders want. He is reportedly still demanding tariff increases, something that won't garner leadership support. He has not abandoned his call for an infrastructure bill. Once Trump's best opportunity to cooperate with Democrats, Breitbart News, newly reunited with former White House chief strategist Steve Bannon, is advising him to attach infrastructure to the Hurricane Harvey relief bill.

In August, the president endorsed an immigration bill sponsored by Sen. Tom Cotton, R-Ark., and Perdue, called the RAISE Act. It would significantly cut annual legal immigration by limiting family sponsorship to spouses and minor children of U.S. citizens creating a point system for employment-based immigration. The RAISE Act seems unlikely to go far in the Senate, but Trump could use the tenuous legal status of the Deferred Action for Childhood Arrivals program for young unauthorized immigrants as leverage to start debate on some of its provisions.

Certainly, Trump wants to show some progress on the border wall, with or without evidence Mexico will eventually pay for it. He will not easily give up on the inclusion of these funds in the fall spending bills and if deterred will bring it up again in 2018, which will be an election year for all 435 members of the House.

Trump isn't going to let up on Congress if nothing significant reaches his desk. Although his own White House is riven by ideological and factional divisions, he is still positioning himself to run against dysfunction in Washington. This could in turn enhance the temptation among some Hill Republicans to wash their hands of Trump, especially in swing districts where the president was never popular.

For this experiment in all-Republican government, a lot is riding on the new few weeks. It's breakthrough or bust.