House Majority Leader Eric Cantor's stunning primary defeat Tuesday was not just a loss for the Republican Party leadership, it was also a blow to pro-immigration activists.

Cantor, R-Va., was widely viewed as a potential broker for a comprehensive reform deal. His loss greatly dims the prospects for that in Congress.

In response, many on the pro-immigration left are furiously trying to spin his defeat, arguing that it isn't also a loss for their side. They have argued that it wasn't really about immigration. Or that if it was, it was because Cantor was too far right. In either case, Cantor's loss is now further proof that the GOP must embrace immigration – despite the fact that he lost the election in large part because Republican voters were upset that he had previously backed reform.

National Immigration Forum Executive Director Ali Noorani took the position that, contrary to most reporting, immigration wasn't the main issue in Cantor's defeat to little-known challenger David Brat.

"Eric Cantor’s loss is about local politics more than immigration. At the same time, he tried to play both sides of the immigration debate, and he got burned," Noorani said in a statement.

On Twitter, Noorani repeatedly pointed to a blog post by RedState's Erick Erickson which argued that Cantor's real problem was that his staff was arrogant and had irritated conservative activists.

Tom Jensen, director of the liberal group Public Policy Polling, also said it wasn't immigration that ended Cantor's career. "He lost because of the deep unpopularity of both himself personally and of the Republican House leadership."

But others on the pro-immigration left said immigration was the issue and Cantor's mistake was that he wasn't consistently pro-immigration. In fact, he would have won if he'd fully embraced the cause, they claim.

"Here's a primary result that makes it absolutely plain: Primaries are won when you don't play politics with your constituents and run on common sense support for immigration reform. Mr. Cantor will lament the day he decided to heed the fears and absurdities of extremists and radio personalities," said Eliseo Medina, chairman of the Service Employees International Union's Immigrant Justice Campaign.

Frank Sharry, executive director of America's Voice, said: "Too bad Rep. Cantor didn't steal a page from Sen. Lindsey Graham, R-S.C., who leaned into the issue, was unapologetic about his principled stand and won his primary handily."

Jim Wallis, founder of the liberal Christian magazine Sojourners, told Politico that Cantor's loss was actually good news for reform fans like himself.

"I did not trust Eric Cantor to be on the right side. Now that he is gone, I am more hopeful that John Boehner can follow his own head and his own heart and do the right thing," Wallis said.

Others are using the opportunity to attempt to simply intimidate Republican voters into backing comprehensive reform. The group Casa de Virginia crashed Cantor's concession speech Tuesday evening, chanting: "What do we want? Immigration reform! When do we want it? Now!" The incident sparked a brief, ugly fracas. The group has a history of these kind of tactics.

In either case, the pro-immigration groups all agreed that the larger message was that Cantor's defeat was proof Republicans must now unequivocally embrace immigration reform to win.

"[Republican leaders] can choose to address the immigration issue head-on and get it resolved, and give the Republican nominee in 2016 a fighting chance in his or her run for the White House. Or they go back to the bunker, sharpen their anti-Obama knives and never get to the White House in the next generation, possibly two," said Rep. Luis Gutierrez, D-Ill.,. in a House floor speech Wednesday.

That's going to be a tough sell to other Republicans. Contrary to Noorani and Jensen, immigration was a key issue in the race and being associated with reform hurt Cantor. Cantor's opponent, Dave Brat, repeatedly called him a supporter of "amnesty" - fighting words in a GOP primary. Conservative talk show hosts Mark Levin and Laura Ingraham regularly slammed the majority leader in the same terms.

Turnout was high in Cantor's suburban Virginia district Tuesday, up 28 percent from 2012. Anyone can vote in Virginia primary elections, not just party members, so some of those votes may have come from Democrats. But turnout was highest in the precincts that voted heavily for Mitt Romney in 2012, suggesting these were mostly energized GOP voters.

The incumbent did not help himself by taking confusing and contradictory stands on the issue. While Cantor signed onto a GOP set of principles in that backed some form of a deal, he also attempted to portray himself as an opponent of amnesty in the primary campaign in an attempt to mollify conservative activists.

The effort may have backfired by keeping the issue front and center while giving Cantor's critics grounds to argue that he was being two-faced.

Cantor's campaign may have alienated those people in his district who do favor immigration reform, but it is doubtful that they voted for challenger Brat, himself a staunch critic. The high turnout suggests that few voters were turned off by the anti-immigration rhetoric and stayed home.

In any event, other Republicans – and even some Democrats in reddish states – are sure to look at Cantor's defeat and see a cautionary tale that critics of immigration are a force that must be taken seriously. That's bad news for the already-fragile comprehensive reform caucus in Congress.