House Speaker Paul D. Ryan (R-Wis.) during a news briefing after a House Republican Conference meeting May 11 on Capitol Hill in Washington. (Alex Wong/Getty Images)

When House Speaker Paul D. Ryan meets Thursday with Donald Trump, his party’s presumptive presidential nominee, he will do so with the widespread support of House Republicans who overwhelmingly elected Ryan their leader six months ago.

But if Ryan and Trump do not quickly move toward reconciliation — as Ryan has already hinted they won’t — the speaker will face immediate and mounting pressure to get behind a Trump candidacy, according to interviews with numerous GOP lawmakers.

Should the two remain at odds, “I think the consequences would be pretty severe, frankly,” said Rep. Kevin Cramer (R-N.D.), one of a handful of early Trump endorsers in the House. “I think they’d be more severe for the institution of the House than it would be for Donald Trump.”

Ryan (R-Wis.) faces a tough task, however. He must hold fast to his own brand of conservatism, and his thinly veiled distaste for Trump’s style and policy positions, but also live up to his responsibility of mending the divides in the House GOP, and the Republican party as a whole, ahead of the general election.

Trump and Ryan are set to meet Thursday morning on Capitol Hill in the office of Republican National Committee Chairman Reince Priebus. Trump will meet later in the day with other congressional leaders, but the meeting with Ryan is under a microscope, given Ryan’s declaration last week, a day after Trump became the presumptive nominee, that he was “not ready yet” to support Trump.

Ryan has sought to tone down his position in recent days, calling his comments part of a process to unite Republicans behind common principles ahead of a tough general election campaign.

“To pretend we’re unified without actually unifying, then we go into the fall at half-strength,” Ryan told reporters Wednesday. “I want to be part of that unifying process so we can go into the fall at full strength.”

Ryan has hinted this week that his meeting with Trump will be less about the businessman’s policy positions — the two differ sharply on trade, immigration and entitlement spending — and more about Trump’s willingness to acknowledge broader conservative principles of government and soften the tone of his campaign.

But Trump, whose anti-establishment campaign has won him nearly 11 million primary votes, appears to be carrying more leverage into the meeting. While both men could benefit from an alliance, several House members said Wednesday that they believe party unity is critical ahead of the convention.

“No ifs, ands or buts,” said Rep. Chris Collins (R-N.Y.), another early Trump endorser, “the party must be united to focus on beating Hillary Clinton.”

Trump, meanwhile, has made it clear that he does not intend to kowtow to Ryan to win his support. “I’m sure I’m going to get along great with him,” he said March 1, after the Super Tuesday primaries. “And if I don’t, he’s going to have to pay a big price.”

After Ryan said last week that he wanted to know whether Trump would be a “standard bearer that bears our standards,” Trump issued a statement saying he was “not ready to support Speaker Ryan’s agenda” — a reference to Ryan’s ambitious effort to assemble a broad legislative platform for Republican lawmakers, and a warning that Trump feels no compunction to take cues from the former vice presidential candidate.

Several House Republicans said Wednesday that they expect Ryan to eventually find a way to support Trump in the months leading up to the Republican National Convention in July.

“Paul Ryan is very principled, but he’s also very professional and pragmatic, and he knows that a big part of his job, the most important part of his job, is leading us and helping us retain our majority,” said Rep. Tom Cole (R-Okla.), a former chairman of the National Republican Congressional Committee. “I don’t see how being at odds with your nominee helps you achieve that objective. So I think, in the end, they’ll find common ground.”

Ryan’s clash with Trump comes as the speaker has been struggling to manage some sharp internal debates among House Republicans. Ryan continues to enjoy widespread goodwill among his colleagues after stepping up to end the leadership crisis prompted by John A. Boehner’s resignation as speaker last year. Even some Trump supporters, such as Cramer, have been willing to give Ryan a wide berth to work out his differences with the presumptive nominee.

But many of those colleagues have thus far been unwilling to take Ryan’s cues on major legislative matters. The House is set to blow past Sunday’s statutory deadline for passing a budget, and a bill Ryan supports to address Puerto Rico’s fiscal crisis remains mired in committee. A prolonged rift with Trump could further undermine Ryan’s ability to lead his caucus.

“We wouldn’t want to add more chaos to the chaos that would already exist,” Cramer said. “But the problem I would see with [an extended Trump-Ryan split] would be a lot of members of the conference would be obviously fractured — further fractured than we already are.”

Rep. Dave Brat (R-Va.) said he would have liked Ryan to have issued “a stronger statement” in support of Trump after clearing the primary field last week. “The people just spoke,” he said. “You need to listen to the people and learn, what are the folks saying to us?”

But asked what would happen if Trump and Ryan remain divided, numerous other members declined to address the consequences — including several members of the House Freedom Caucus, who led the opposition to Boehner.

“We’ll just see what they say,” Brat said.

“I don’t want to talk about contingency plans yet, because I think it’s way premature, and I think [Ryan’s] going to come to grips,” said Rep. Matt Salmon (R-Ariz.).

“I think that’s very unlikely,” said Rep. John Fleming (R-La.). “I just believe that Trump will want to be successful. He’s a dealmaker, so he wants to find a resolution.”

“I don’t think it will be an issue,” said Rep. Ted Yoho (R-Fla.). “I think everybody will be on the same page going into the convention … lest some unforeseen wild card shows, which I don’t see happening.”

Kelsey Snell contributed to this report.