What would it take for Republicans to break ranks en masse and start to publicly question the direction of the party and President Trump’s leadership?

On Monday night, the Senate bill to repeal and replace Obamacare died before it hit the Senate floor, making it look like a key part of Trump’s legislative agenda may fail. New questions keep arising about the Trump campaign’s relationship with Russia. The federal courts regularly rebuke key aspects of his immigration orders. Most Americans believe his use of Twitter is “unpresidential.” The president has unusually — even historically — low public approval.

And yet the president remains popular with Republican voters. In the most recent Gallup tracking poll, 87 percent of self-identified Republicans said they approved of the job he’s doing. What might change that?

To answer this question, it helps to look into the social psychology of group loyalty. Consider politics today as populated by two tribes: Democrats and Republicans. A growing literature suggests that partisanship has become a social identity akin to tribal affiliations, inspiring strong loyalty.

But people can and do, on occasion, dare to voice opinions out of line with their party’s stance on an issue. What pushes them to break ranks?

Here’s how we did our research

We have published data that provide some clues. In 2013, we asked 214 self-identified Republicans on Amazon’s MTurk (a crowdsourcing platform used by social scientists to conduct surveys and experiments) how willing they would be to publicly express views that diverged from the Republican Party’s position on Obamacare — by speaking out to a group of Republicans, posting on a blog, even calling into conservative talk radio. In 2014, a second sample of 303 self-identified Republicans on MTurk rated how willing they would be to express views that diverged from the Republican Party’s position on military intervention in Syria.

In the Obamacare study, we asked respondents whether they privately disagreed with the Republican Party’s position. We also measured how much they felt a sense of connection to the Republican Party. And we asked how concerned they were that their party’s stance on the issue would undermine its ability to win elections. All three mattered.

The three measures combined to predict how willing a respondent said he or she would be to publicly disagree with the GOP’s position on the Affordable Care Act. First, people had to actually disagree with the Republican Party’s position. Although most of our participants were aligned with their tribe, a sizable minority had qualms.

But disagreement by itself did not translate into willingness to publicly express apostate views. Individuals also had to identify strongly with the Republican Party. People who don’t feel particularly connected to their party can easily tune out, disengage and keep their concerns to themselves. But strongly identified party members feel an obligation to the group, a sense that even when dissent is personally risky, they cannot give up on the party.

And so in our survey, Republicans who felt strongly connected to their party reported greater willingness to speak out against their party’s position.

Counterintuitively, the strongest partisans are most likely to criticize the party’s positions

This might sound counterintuitive, since the people with the strongest partisan loyalties are also most likely to adopt party leaders’ positions on issues. But here’s what makes the difference: People who felt connected to the party were willing to express opposition only if they felt that their party’s position threatened the future of the Republican Party and its ability to win elections.

In other words, strongly connected Republicans were willing to speak out when they worried that their tribe’s future was in jeopardy.

Social psychologists call these sorts of concerns “collective angst.” Republicans are not alone in feeling collective angst. Members of many groups — including French Canadians, Israelis and Americans — experience collective angst. And for good reason. In the political context, parties rise and fall, come and go. When was the last time anyone voted for a Whig or Know-Nothing?

We observed similar effects in our second study, which focused on the Republican position that the United States should intervene militarily in Syria. We experimentally manipulated feelings of angst by highlighting poll data that would induce either concern or confidence about how the Republican Party’s position would influence its ability to win the next presidential election.

And indeed, we found evidence that collective angst can prompt political dissent. Individuals who identified strongly with the party were more willing to speak out only if they received the troubling polling data.

To be sure, Trump already has some prominent Republican critics: Sens. Lindsay O. Graham (S.C.) and Susan Collins (Maine) and The Weekly Standard’Bill Kristol, among others. But so far, overall, there’s not very much open intraparty dissent among party elites — and few Republican voters are abandoning their loyalty.

That could change. As political scientist John Aldrich has argued, when parties no longer serve the interests of ambitious politicians, elites and then voters will abandon them.

Full-scale breaking of ranks will depend on growing angst about party interests and the long-term viability of the Republican brand.

Editor’s note: An earlier version of this post identified Bill Kristol as a contributor to the National Review. Kristol is also founder and editor at large of the The Weekly Standard. We regret the error. 

Dominic Packer is associate professor of psychology and associate dean for research and graduate programs in Arts & Sciences at Lehigh University.

Michael Wohl is professor and graduate chair in the department of psychology at Carleton University.