Hillary Clinton’s veepstakes is ending the way it began: with the humble-but-sturdy Tim Kaine sitting at the top of her list.

After an extensive, months-long process during which the campaign considered a host of different options -- even vetting a serious candidate from outside the political arena -- the squeaky-clean Virginia senator, whose biggest liability to emerge was that he was boring, is emerging as Clinton's top choice. Kaine has been urged along by two men familiar with the demands of the job: President Barack Obama and former president Bill Clinton, those close to the process say.

And after Donald Trump’s somewhat more polished performance Thursday night, even Democrats who had been pushing for a flashier choice like Massachusetts Sen. Elizabeth Warren or New Jersey Sen. Cory Booker were sobered by the challenging four months ahead. “After last night, she needs to make the safest choice possible,” said a former senior White House aide.

“Safe” seems to be Kaine’s middle name. The Spanish-speaking former missionary and onetime swing-state governor sits on both the Armed Services and Foreign Relations committees in the Senate. And while the Warren-Sanders wing of the Democratic Party may object to some of his positions on trade and Wall Street regulation, Kaine rarely takes controversial stands or makes painful gaffes, thus fulfilling the Hippocratic oath for vice presidential nominees: First, do no harm.

Kaine, for all the buzz about his chances, has been deeply self-effacing during the awkward public tryout process. When asked during a “Meet the Press” interview last month if he was ready to be president, he said no. "Nobody should ever say they’re ready for that responsibility, because it is so, so huge,” he said in what some saw as a tacit rebuke of Warren, who answered confidently that she is ready to be commander in chief when asked the same question by Rachel Maddow.

But Kaine's humble, vanilla persona endeared him to Clinton. “I love that about him,” she told CBS News’ Charlie Rose in an interview earlier this week when grilled about whether he was too boring. Added Virginia Gov. Terry McAuliffe, a close confidant of the Clintons who has been pushing for his home-state senator: “If anything, he’s only helped himself through this entire process.”

In addition to McAuliffe, President Obama and Bill Clinton have also privately or publicly expressed their support for Kaine, who was passed over for the No. 2 slot in 2008. Earlier this week, White House press secretary Josh Earnest, unprovoked, told reporters that Kaine was someone Obama believes would be a good pick for Clinton. “Senator Kaine was one of the first public officials to announce a public endorsement of Senator Obama,” he said. “Senator Kaine served as the chair of the DNC during President Obama’s first year in office, and Senator Kaine is somebody that the president deeply respects.”

Bill Clinton, who has been deeply involved in the process, had also been pushing for two people, but ultimately “Tim is his first choice,” said a source close to the former president. “The advice he gives is much more: Here are the issues you’re going to have; here’s why you need this person. It’s more from experience.”

“Hillary Clinton would feel very compatible working with someone like Tim Kaine,” McAuliffe told POLITICO in a recent interview. “He’s a very thoughtful, quiet negotiator -- he doesn’t really care about the limelight. She’s worked with folks like Tim for years. He’s in it for the right reasons -- he didn’t jump at the chance to run for the United States Senate. He was perfectly happy to go be a university professor. He doesn’t have to do this for the big rah rah -- he can really help people. It’s unique for a lot of folks.”

The prospect that McAuliffe would fill Kaine’s Senate seat also boosted his chances over another appealing choice to the progressive wing of the party, Ohio Sen. Sherrod Brown, whose seat would be filled by Republican Gov. John Kasich.

But McAuliffe said that Clinton likes Kaine’s “worker bee, gets things done” style. “He brings people in. He doesn’t say, ‘This way or the highway’ -- he tries to structure compromise,” he said.

Clinton kept her vetting process tight among top aides such as Cheryl Mills and John Podesta. Earlier this week, South Carolina Rep. Jim Clyburn said he had been consulted by the Clinton campaign to discuss Kaine, as well as Labor Secretary Tom Perez and Agriculture Secretary Tom Vilsack. “I’ve had more experience with Tim Kaine than all the three,” Clyburn told reporters. “The three finalists who I understand are the three finalists ... I admire a whole lot.”

As the veepstakes winds to a close, Kaine is keeping his cool. Rep. Gerry Connolly (D-Va.) said he bumped into Kaine at a “small, intimate dinner party last night” and that he wasn’t able to pry any information out of him.

“He seemed quite normal and enjoyed himself and was relaxed and had not heard anything,” Connolly said in an interview Friday morning.

Kaine’s biggest liability, aside from his personal view against abortion, may be his middle-of-the-road stances on trade deals and financial regulations – positions that put him at odds with the ascendant left wing of the Democratic Party.

"Every progressive I talk to is concerned both about Kaine’s history of trade cheerleading and that this portends Clinton is going to surround herself generally with cautious centrists who don't like ruffling feathers with big corporations," said a progressive Democrat. “The economic anger that exists somehow still hasn't affected her decisions, which is scary, depressing, and provocative.”

There is also the possibility that Clinton turns instead to Vilsack, someone for whom she has great personal affinity. The agriculture secretary, a popular former governor of swing-state Iowa, also had a lot of backers pushing him internally. Former Pennsylvania Gov. Ed Rendell, who has been in constant communication with the Clinton campaign over convention planning, was pushing for Vilsack, the first member of Obama’s Cabinet to endorse Clinton in 2015.

A source close to the campaign said that as of Thursday, Clinton operatives involved in the process were still talking about Vilsack as a serious possibility. Booker and Admiral James Stavridis, a former NATO commander who emerged as a dark-horse contender from outside the political arena, were also still on the list in the final days.

As for Warren, she apparently believes she is out of the running, telling “Late Show” host Stephen Colbert on Thursday night: “I think if it were me, I would know it by now. So probably not.”

Clinton has been off the trail, holed up at her home in Chappaqua for the past two days. She is expected to make her announcement on her final trip before the convention, a two-day swing through Florida beginning Friday afternoon.

**Gabriel Debenedetti and Burgess Everett contributed to this report.