Republican presidential candidate Donald Trump, photographed in Iowa in January, is closing in on his pick for a vice-presidential running mate. (Charles Ommanney/The Washington Post)

Closing in on his choice for a running mate, Donald Trump spoke favorably Monday about tapping an experienced politician over a political outsider to help reassure and unite the fractured Republican Party.

Trump, who is slated to be nominated for president at the Republican National Convention in Cleveland next week, plans to announce his choice later this week. His allies say he favors a trio of elected leaders: Indiana Gov. Mike Pence, New Jersey Gov. Chris Christie and former House speaker Newt Gingrich (Ga.).

Trump’s preferences have evolved in recent days as he contemplated what could be one of the most consequential decisions of his campaign.

He was intrigued late last week by retired Lt. Gen. Michael T. Flynn, telling friends that a military pick would signal strength and steadiness — and even testing out how “Trump-Flynn” sounded as a brand name.

But Flynn’s stock fell after a shaky interview with ABC News on Sunday in which he stated his support for abortion rights, a position sure to spark a revolt at the Republican National Convention. On Monday, however, Flynn told Fox News Channel that he is a “pro-life Democrat.”

New Jersey Gov. Chris Christie gestures as he introduces Republican presidential candidate Donald Trump at a rally in Virginia Beach, Va., on Monday. (Steve Helber/Associated Press)

By Monday, Trump suggested that he was moving away from the idea of a general.

“I do like the military, but I do very much like the political,” Trump said in an interview Monday with The Washington Post’s Fix blog. “I will make my mind up over the next three to four days. In my mind, I have someone that would be really good.”

Trump was careful not to eliminate Flynn, but explained his reasons for prioritizing political experience over military credentials. “I have such great respect for the general, but believe it or not, that will be one of my strong suits,” he said. Second, he added, he sees picking a politician as a way to bring his party together for the fall campaign.

“I don’t need two anti-establishment people,” Trump said. “Someone respected by the establishment and liked by the establishment would be good for unification.”

That conclusion has been underscored by several of Trump’s confidants, including campaign chairman Paul Manafort, who has counseled Trump to pick a seasoned conservative leader, according to multiple people familiar with the discussions.

Manafort, who has operated within the GOP establishment for decades, is aware of how raw tensions remain about Trump’s candidacy. According those in communication with the campaign, Manafort thinks that the vice-presidential pick could be a reassuring gesture to those party elites who are wary of, if not outright hostile to, Trump.

Several of Trump’s adult children — daughter Ivanka and sons Donald Jr. and Eric, along with Ivanka’s husband, Jared Kushner — have been privately advising their father about his choice and also favor an experienced hand, such as Gingrich or Pence, according to people close to Trump, who spoke on the condition of anonymity because they were not authorized to discuss the deliberations publicly.

These people cautioned that Trump often is unpredictable and that he could continue to change his mind until he makes a final decision. They said he was genuinely undecided over the weekend as he socialized with friends and raised money in the New York area.

Republican leaders, who have begun gathering in Cleveland for meetings before the convention opens Monday, are nervously anticipating Trump’s selection.

“I think he would be wise to go to somebody who has a résumé and background that feels more comfortable as a governing person,” said Thomas D. Rath, a longtime New Hampshire-based GOP figure. “He does not need a hot personality.”

Rath drew historical analogies to George W. Bush’s selection of Richard B. Cheney and Barack Obama’s pick of Joseph R. Biden Jr., noting that in both cases the presidential nominees were relatively new to the national scene and tapped Washington veterans to round out the tickets.

A successful vice-presidential launch could help Trump make up ground after a series of self-inflicted mistakes over the past two months eroded some of his public support, said Steve Schmidt, a longtime GOP presidential campaign strategist.

“If you’re the outsider candidate, the vice-presidential selection says a great deal about your campaign, your values and how you intend to govern,” he said. “Trump has said that he’s going to have the best people working for him and that the American people have been victimized by a professional political class of losers. He’s going to need to pick somebody that fits the model of ‘the best.’ ”

Trump demonstrated an easy rapport with Gingrich on the campaign trail last week, leading close observers to think he would be the pick. But people close to Trump said that Christie and Pence’s stock has been rising as well, and that as of Monday all three were real possibilities.

Christie met privately on Saturday with A.B. Culvahouse Jr., the lawyer leading Trump’s vetting process, to discuss his record in New Jersey, including a bridge-closing scandal in 2013 that roiled his administration, according to two people familiar with the process.

Christie — one of Trump’s earliest and most loyal supporters in the primaries who has been managing his presidential transition project — campaigned alongside Trump on Monday in Virginia Beach, Va. A former federal prosecutor, he enthusiastically played the role of attack dog, ripping into likely Democratic nominee Hillary Clinton, and showed that he would bring law-and-order machismo to the Trump ticket.

Pence will have his chance at a public audition Tuesday, when Trump visits Indiana to raise money and hold a rally in the Indianapolis suburb of Westfield. Trump does not know Pence as well as he does Christie, although Pence’s visit with the candidate at one of Trump’s golf clubs in Bedminster, N.J., this month was described as friendly and warm.

Trump will head to California on Wednesday for a string of fundraisers, and Friday is considered a possible date for a vice-presidential announcement, although advisers said Trump could reveal his choice at any point this week.

All three prospects would bring baggage to the ticket. Gingrich, after decades in the national spotlight, has collected enemies and come under scrutiny for his for-profit ventures since leaving the House in the late 1990s. Christie is deeply unpopular at home and would have to defend not only his handling of the “Bridgegate” affair, but also New Jersey’s poor fiscal condition. And Pence has had a rocky first term in the governor’s office, most notably coming under criticism for a state religious-liberties law that is considered discriminatory against gays.

Hovering around the process is Sen. Jeff Sessions (Ala.), another early Trump backer who is a central force in the campaign and is said to be ready to serve as Trump’s running mate if asked.

Christie’s close relationship with Trump has elevated him in the search process. The governor is a frequent presence in the 26th-floor executive suite at Trump Tower, where the candidate works, and speaks regularly with him by phone. Meanwhile, Christie associates, including his brother, Todd, and his confidant William Palatucci, are working with Trump’s political operation.

“Trump appreciates loyalty — always has — and he appreciates that Chris was one of the first major figures in the party who came over and endorsed him,” said former GOP New Jersey governor Thomas H. Kean.

Rucker reported from Cleveland. Chris Cillizza in Washington contributed to this report.