Cliff Owen / AP

Among the many achievements of Mike Pence’s strong performance in Tuesday’s vice-presidential debate was that for long stretches he made it unusually possible to envision how Republicans might effectively govern if Donald Trump wins the presidency. But the very manner of Pence’s success hinted at the tension and division that would more likely ensue if Trump overcomes his deficit against Hillary Clinton.

Pence performed so well because he systematically linked Trump to mainstream conservative thinking on economic, social, and foreign-policy issues. The Indiana governor, a former leader of House conservatives, made the classic Ronald Reagan small-government argument for lower taxes and less regulation more crisply and confidently than Trump has ever done. “Donald Trump and I,” Pence insisted, “have a plan to get this economy moving again just the way that it worked in the 1980s.” In the debate’s final moments, Pence offered an impassioned affirmation of the social conservative case against abortion rights. And on foreign policy he again portrayed Trump as a return to Reagan’s vision, promising the nominee would deliver “peace through strength.” In all, Pence situated Trump squarely in the mainstream of ideas that most Republican office-holders have championed for years.

But, as many commentators quickly noted, Pence managed that only by strenuously ignoring much of what Trump has actually said during his mercurial career. In the process, Pence also wished away the disruptive and discontented forces in the GOP coalition that powered Trump’s nomination.

Repeatedly, Pence softened what Trump has said, ignored it, or, when cornered, simply denied it. Though Pence forcefully prosecuted the case for change, the cumulative impression he left was that he did not defend so much of what Trump has said because he too considered it indefensible.

In fact, on that front, the evening could have been even tougher for Pence. Tim Kaine pressed Pence primarily about Trump’s praise of Russian leader Vladimir Putin and his derogatory comments about women and undocumented Mexican immigrants. Kaine repeatedly tied Pence in knots simply by asking him to defend Trump’s own declarations on issues such as NATO’s future role and the advisability of more nations, like Saudi Arabia and Japan, obtaining nuclear weapons. That allowed Kaine to frequently take the offense, despite his lackluster defense of President Obama’s record and Clinton’s agenda.

Pence’s frequent inability or unwillingness to defend his running mate’s plain words on Putin or nuclear proliferation foreshadowed how difficult it would be for congressional Republicans to follow Trump down those roads if he wins. Yet all of that only scratched the surface of issues that would divide a President Trump, and the heavily blue-collar voters who elevated him, from most congressional Republicans and the GOP’s key business supporters.

For a more complete list, a good place to start is my conversation with House Speaker Paul Ryan last week at the Washington Ideas Forum co-sponsored by the Aspen Institute and The Atlantic. In the interview, Ryan did his best, as throughout the campaign, to avoid discussing Trump while highlighting the “Better Way” agenda that House Republicans have crafted. And Ryan made a genuine plea for voters to provide Republicans unified control of Congress and the White House.

But when I asked Ryan about Trump’s threat to withdraw from the North American Free Trade Agreement if Mexico and Canada do not substantially renegotiate it, he crisply demurred: “Let's work on improving and not talk about withdrawing [from] it.” When I asked if Ryan would drop his plan to convert Medicare into a premium support system or to reform Social Security because Trump has repeatedly said he opposes any changes in the programs, the speaker made clear he would not. “If we blow another presidency and don't fix these entitlement problems and then get around to it after the boomers are well under retirement, it will be ugly reforms that pull the rug out from under people after they're retired,” he said.

Ryan was equally dismissive of Trump’s promises to spend even more on infrastructure than the $275 billion plan Clinton has proposed. “That's not in the Better Way agenda,” he said, laughing. As throughout the campaign, Ryan rejected Trump’s plan to accelerate deportation of the estimated 11 million undocumented immigrants: “I think there is a way to deal with the undocumented population that doesn't involve mass deportation.” And though Ryan wasn’t familiar with Trump’s call to limit legal immigration to restrict the total share of the U.S. population born abroad, the speaker’s initial reaction was skepticism: “I’ve never looked at it like that.” While Trump has stressed “law and order,” Ryan reaffirmed his support for criminal-justice reform.

In that litany, Ryan opposed most key components in the bristling insular populism that Trump used to build a winning primary coalition centered on working-class whites. Trump’s enthusiasm for entitlement and infrastructure spending, his hostility to international trade and foreign alliances, and his provocative positions on immigration and crime, all reflect priorities of the party’s growing blue-collar wing. Yet to Ryan, many other Republican legislators, and much of the party’s business leadership, those positions are economically irresponsible, racially indefensible, and politically suicidal.

If Trump won and attempted to implement his agenda, the fractures in the GOP would be much more jagged than Mike Pence allowed in the airbrushed portrait of unity he painted Tuesday night. That prospect is one key reason so many GOP leaders are privately debating whether the party would face greater long-term risk from a Trump defeat—or victory.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.