While Kaine, a former governor himself, is still widely regarded as the front-runner for the job by those in attendance, a handful of Vilsack’s fellow current and former Midwestern governors advocated for him behind closed doors during the proceedings, and the secretary himself suggested in conversations there that he was under serious consideration, according to individuals familiar with the discussions.

The timing of the surge of attention couldn’t come at a better time for the man who has been recently increasing his national media presence through a series of interviews and public events as a surrogate. Over the weekend, he went so far as to defend his foreign policy chops during a Sunday show appearance.

Clinton is likely to announce her pick in the coming days, almost certainly in the time between the Republican convention and her own — and possibly during her first general election campaign trip to Florida on Friday and Saturday, to minimize any bump in the polls Trump receives from his Cleveland convention.

The presumptive Democratic nominee has increasingly been appearing with her vice-presidential hopefuls in the days leading up to that moment, including Kaine on Thursday and Ohio Sen. Sherrod Brown on Monday, and the candidate and a gaggle of her top aides spent Friday at her Washington home to go over her options.

A handful of them — including Housing Secretary Julián Castro, Massachusetts Sen. Elizabeth Warren and Colorado Gov. John Hickenlooper — stopped by for in-person meetings, as Clinton has sought to get to know them better.

That’s not a concern for Vilsack, the single prospect who has had a long personal relationship with the former secretary of state, dating back decades before they served four years in the same Cabinet. That relationship has bolstered his boosters’ case for him in recent days, but they also note that he could stand to play a significant role as Clinton courts white working-class men — especially in rural areas — in the Midwest, a constituency she and her husband, former President Bill Clinton, are particularly concerned about as Trump targets them.

Clinton largely lost blue-collar white men to Bernie Sanders in the primary, and a Washington Post/ABC News poll released last week showed that 75 percent of white men hold an unfavorable view of her.

Vilsack demurred on Monday when POLITICO asked whether he is currently going through Team Clinton’s vetting process — “Has anyone ever answered that question?” he shot back — but he did speak in general terms about the factors that are fueling his apparent rise.

“I’m a workhorse, not a show horse,” said the former two-term governor, who has long been rumored as a potential chief of staff in a Clinton White House, echoing a line that the candidate herself often uses when talking about her work in the Senate. “Not a rock star; I’m rock solid. I’m all about doing, and getting things done. It’s not in my nature to market myself. My nature is to market what we’re doing in my department, and in my state. I don’t know if that’s the reason, but we work hard down here, and we get things done."

Vilsack’s trail presence for months has been more focused on lavishing praise on Clinton. Last August, for example, Vilsack’s adoration for Clinton was on full display as he introduced her in Ankeny, Iowa, before she unveiled her rural policy platform — which he helped craft. He listed all of her accomplishments and talked about their friendship and their shared political history. His 15-minute introduction of the former secretary of state was so complimentary it was almost overkill.

“I will and my wife will always remain loyal to our friend, Hillary Clinton,” said Vilsack, the longest-serving member of the Cabinet, who’s traveled to all 50 states in that capacity but maintained a relatively low national profile,

“Talk about somebody who studies a problem, asks for advice about what will work, puts together teams, collaborates and then delivers,” Clinton said as she took the stage. “He is exhibit A.”

Yet after the presumptive Republican nominee tapped the little-known Pence over the bomb-throwing former House Speaker Newt Gingrich and New Jersey Gov. Chris Christie on Friday, many Democrats’ concern about the need for a sharp-elbowed running mate dissipated, figuring that a relatively fireworks-free Pence-Kaine or Pence-Vilsack debate would not be likely to harm Clinton’s chances.

A relatively low-key public profile, after all, ranks low on the list of running-mate concerns compared to the prospect of losing an Ohio Senate seat to Republicans if Clinton were to choose Brown. And Vilsack supporters insist he could be a net positive on the campaign trail if he began talking more about his own background, starting with his early life in a Pittsburgh orphanage.

Clinton is aware, however, of the perception that by choosing someone like Kaine or Vilsack she would be playing it safe — one reason her campaign has been happy to maintain a sense of unpredictability by keeping a long list of hopefuls in the public discussion.

Still, sketching out the electoral map, people close to Clinton see Vilsack as a potentially useful tool as they court both the voters who eluded her during the primary and those of Iowa, a crucial swing state.

“I believe he’s always been in the circle of people that not only Hillary is considering, but I’m sure her advisers, including Bill, and others see [as] a viable running mate,” explained former Iowa Sen. Tom Harkin, also pointing to Vilsack’s roots in Pennsylvania, another likely battleground. “He’s someone who can relate to white men in rural areas, small towns and communities."

“I don’t want to compare myself to other people [in contention for the job], but I will tell you I’ve spoken with so many groups and I’ve represented those folks as a small-town lawyer, as a small-town mayor, as a state senator, then representing the state. I understand those folks and their struggles,” Vilsack said. “In this particular election, given the uneasiness people have about Mr. Trump in small towns where I’ve been working, there’s an openness [to Democrats].”

People in contact with Clinton’s inner circle often note that the former secretary of state and first lady — having seen two president-vice president relationships up close — is eager to find someone she can easily work with, and Vilsack’s long history with both the candidate and Bill Clinton is likely a point in his favor.

They first met over 40 years ago, when Hillary Clinton and Vilsack’s late brother-in-law, Tom Bell, worked together on the Senate Watergate Committee. They grew closer during Bill Clinton’s White House tenure, when she helped his 1998 campaign that made him Iowa’s first Democratic governor in three decades — Christie Vilsack, who works as a top official at U.S. Agency for International Development, often tells friends about the time she and her husand stayed in the White House in the late 1990s, when he was still in the Iowa state Senate. The Vilsacks and then-President Bill Clinton stayed up until the wee hours of the morning visiting over Diet Cokes.

After Vilsack ended his own short-lived 2008 presidential bid, he became a top surrogate for then-Sen. Hillary Clinton in her race against Obama.

Vilsack has already quietly been involved with her campaign in recent months, and they still speak regularly, said people close to them both: In early 2015, he directly urged Clinton to install Matt Paul — his longtime aide, and now one of Clinton’s senior traveling advisers — to run her team in Iowa after hearing that she was leaning in another direction.

The one big political blemish Vilsack has on his record is the 2010 firestorm over his firing of Shirley Sherrod, a Georgia USDA official whom the late Andrew Breitbart had accused of making racist statements that were quickly debunked. The Obama administration later apologized and offered Sherrod her job back, though she declined the offer.

The current chairman of the House Agriculture Committee, Mike Conaway, a Republican from Texas, praised Vilsack — even though he’s supporting Trump.

“He’s a capable guy. I give him good marks for what he did as secretary of ag for 7½ years,” Conaway told POLITICO. “It’s not surprising that someone of his caliber and quality would be on her shortlist.”

**Catherine Boudreau and Ian Kullgren contributed to this report.