WASHINGTON — Anxiety over Donald Trump spread Monday among congressional Republicans, pushing several to follow House Speaker Paul Ryan's lead and withhold their support from the divisive billionaire. Ryan himself declared there's no point in trying to “fake” party unity.

“If we go forward pretending that we're unified, then we are going to be at half-strength this fall,” Ryan told The Journal Times in Racine, Wis., defending his decision last week to refuse to endorse his party's presumptive presidential nominee.

Still, in interviews with home state reporters Monday, Ryan denounced the idea of any Republican launching a third-party or independent candidacy to challenge Trump, telling the Milwaukee Journal Sentinel it “would be a disaster for our party.”

And Ryan said he'd step aside from the House speaker's traditional role as chairman of the Republican National Convention if Trump wants him to, a scenario that Trump left open over the weekend.

“He's the nominee. I'll do whatever he wants in respect to the convention,” Ryan said.

Trump shrugged off the need for unity heading into the November general election and a likely matchup against Democrat Hillary Clinton.

“I think this is a time for unity. And if there's not going to be unity, I think that's OK, too,” Trump said on Fox Business Network. “I mean, I'll go out and I think I'll do very well. I think I'm going to win the race either way.”

The comments from Ryan and Trump came as both men prepared for a meeting Thursday. Trump will meet Thursday with Senate Majority Leader Mitch McConnell and other Senate GOP leaders.

Ryan's negative stance appeared to be providing cover for some vulnerable Republicans eager to distance themselves from Trump and his controversial comments about women, Latinos, prisoners of war and others.

Pennsylvania Sen. Pat Toomey, one of the most endangered Senate Republicans, wrote an opinion piece in the Philadelphia Inquirer in which he drew back from his long-stated intent to back the GOP nominee.

“His vulgarity, particularly toward women, is appalling. His lack of appreciation for constitutional limits on executive powers is deeply concerning. In short, I find his candidacy highly problematic,” Toomey wrote. “There could come a point at which the differences are so great as to be irreconcilable.”

Toomey appeared to be the only Senate Republican running for re-election to publicly step back from plans to vote for Trump. But other backing has come with little enthusiasm as senators have announced in the same breath plans to skip the July convention in Cleveland.

Several newly elected lawmakers who could face difficulty in November, including Reps. Martha McSally of Arizona, Will Hurd of Texas and Barbara Comstock of Virginia, have told local publications they are not ready to back Trump.

Trump's tendency to shift stances on policy issues arose anew Monday as he defended a weekend suggestion that his tax plan could be negotiable. Clinton aides pounced on the issue in a conference call while Trump defended himself, saying, “This is a negotiation.”

Ever confident, Trump announced that New Jersey Gov. Chris Christie, a former foe but now a supporter, would head his transition team if he wins the White House.

Another former opponent, Sen. Marco Rubio of Florida, who's been mentioned by Trump as a potential vice presidential pick, issued a statement saying he wasn't interested because Trump “will be best served by a running mate and by surrogates who fully embrace his campaign.”