As he tries to recover from a series of stumbles ahead of an important primary contest next week in Wisconsin, Republican presidential front-runner Donald Trump made a surprise appearance in Washington on Thursday and presented himself as the presumptive leader of his party.

He met with his foreign policy advisers, huddled with Republican National Committee Chairman Reince Priebus and predicted that he would bring harmony to the fractured GOP.

“Looking forward to bringing the Party together — and it will happen!” Trump wrote on Twitter shortly after his RNC meeting.

When asked about the meeting during an interview with Fox News, Trump called the party officials “very good people.” Two days earlier, Trump had backed away from an earlier party loyalty pledge and complained about being treated “very badly” by the GOP.

He called Thursday’s session a “terrific meeting” and a “unity meeting,” according to a transcript of the interview.

The Fix's Aaron Blake breaks down what's at stake for the GOP candidates in the April 5 Wisconsin primary. (Peter Stevenson/The Washington Post)

Trump’s Washington visit came as his efforts to secure the nomination have encountered growing turbulence and the GOP remains in disarray.

Anti-Trump forces in the party are frantically maneuvering to defeat the New York billionaire in Tuesday’s Wisconsin primary, which is shaping up as a crucial moment in the battle for the GOP nomination.

A Trump loss to rival Sen. Ted Cruz of Texas would increase the likelihood of a contested convention in July, which Trump critics hope could ultimately deny him the nomination.

If he loses Wisconsin, “he would have to completely run the table [in the remaining contests], and I don’t think that’s going to happen,” said Katie Packer, director of Our Principles PAC, an anti-Trump group. She was referring to what would be necessary to get the 1,237 delegates needed to win the nomination on the first ballot.

Until recent days, Trump appeared to be gaining strength against his GOP opponents, amassing delegates, rising in the polls and continuing to draw large crowds to his rallies. But new controversies — including a battery charge against his campaign manager for roughing up a reporter and Trump’s statement this week that women who receive illegal abortions should be punished — threatened to thwart his momentum.

The party also appeared to be fraying beyond repair, with Trump, Cruz and the third remaining presidential candidate, Gov. John Kasich of Ohio, all backing away this week from their pledges to support the eventual GOP nominee.

A Wisconsin poll released on Wednesday suggested trouble was brewing in that state for Trump.

The survey, by Marquette Law School, said that Cruz had surged to 40 percent support among likely voters, up 21 points since February — enough to give him a 10-point lead over Trump.

Wisconsin should be favorable terrain for Trump. The state is home to a large contingent of Republican voters without college degrees, a demographic that has backed him.

Forty-two delegates are at stake in Tuesday’s primary, allocated in a hybrid system based on victories in congressional districts and the statewide vote.

Much of Wisconsin’s Republican establishment, led by Gov. Scott Walker, a onetime presidential candidate, has rallied around Cruz as the best hope of defeating Trump.

In an interview Thursday, Walker pointed to the support Cruz has been receiving from the state’s popular conservative radio talk show hosts as a key factor in giving the Texas senator the ability to compete against Trump.

Walker said Cruz is the only candidate who can clear the primary and also win the general election.

“Arguably, there are two candidates who can mathematically win the nomination,” he said. “There are two candidates who have a shot at beating Hillary Clinton. Ted Cruz is the only one in both categories.”

The impact of the radio hosts came into clear view during a sweep of Trump interviews earlier this week. Trump struggled in responding to avowed anti-Trump radio host Charlie Sykes, who has enormous influence among conservatives in the state. Sykes hammered the candidate on the tone of the campaign, homing in on Trump’s recent feud with Cruz, during which Trump ignited accusations of misogyny after he reposted an unflattering image of Cruz’s wife, Heidi.

“I expect that from a 12-year-old bully on the playground, not somebody who wants the office held by Abraham Lincoln,” Sykes said.

In his appearances this week in Wisconsin, Trump irritated some conservatives by seeming to mock two of the state’s favorite sons, Walker and House Speaker Paul D. Ryan. His harshest comments came during an appearance in Janesville, Ryan’s hometown.

Trump dismissed Walker’s support for Cruz and poked fun at the governor’s obsession with Harley-Davidson motorcycles.

“The motorcycle guys like Trump,” Trump said. “And he doesn’t look like a motorcycle guy to me, I’m sorry.”

When Trump asked attendees how they liked Ryan, “your new speaker,” the crowd responded with boos and jeers.

A loss in Wisconsin would not necessarily affect the outcomes of future states. The next big contest is Trump’s home state of New York, where he is favored to win. A string of primaries in East Coast states in April could pad his delegate lead. The next Midwest contest, in Indiana, is not until May 3.

Still, Trump made clear during his Janesville rally this week that he does not intend to lose.

“I’m not going to let anything happen in Wisconsin,” he said. “We have to win. Look, we have to put these politicians in their place, folks.”

Dan Balz, Scott Clement and Dave Weigel contributed to this report.