Sen. Tim Kaine of Virginia has emerged as a leading contender after a methodical search, several Democrats close to the campaign say, receiving spirited backing from President Barack Obama and former President Bill Clinton.
In selecting the battleground of Florida to make her public announcement, Clinton is hoping to seize the spotlight from Republicans after their convention in Cleveland. She is set to visit Orlando and Tampa on Friday, but her new partner is not expected to join her until Saturday at a rally here at Florida International University, where the student body is more than half Hispanic.
Kaine speaks fluent Spanish, and last week, Clinton beamed at a Virginia rally as he declared: "Estamos listos para Hillary!" or "We are ready for Hillary!"
Clinton has yet to reveal her choice beyond her tight inner circle, fearful of it leaking before a well-orchestrated weekend rollout is set into motion. Her campaign, looking to build their email and text list, has offered supporters the chance to be the "first to know" their vice presidential pick, much like Barack Obama did in 2008.
The focus of her search in the final days also centers on Agriculture Secretary Tom Vilsack, according to several Democrats close to the process, confident either Kaine or Vilsack would fit her chief criteria of being a strong governing partner and ready for the presidency.
"She's not going to be waffling at the 11th hour like (Donald) Trump," one Democrat close to the process said, speaking on condition of anonymity because of the secrecy surrounding the selection. "By now, she knows who she wants and will be confident in her choice."
She also was considering Labor Secretary Tom Perez, who would be the first Hispanic candidate on the party's ticket, or Sen. Cory Booker of New Jersey, who would be the first African-American vice presidential nominee. Democrats close to the process said Perez and Booker had considerable strengths, far beyond their diversity, but their limited experience in national security and government made them less likely to be selected.
The Clinton campaign watched the closing day of the Republican convention
with great interest, particularly Trump's speech
, but decided against making an announcement early Friday morning. Her campaign is trying to rally excitement around the Democratic ticket heading into the party's convention next week in Philadelphia.
The consensus, even among several Democrats close to other finalists, is that Kaine will be tapped as Clinton's vice presidential candidate. Yet others close to Clinton still cautioned against counting out Vilsack, who has the most state and federal governing experience and the longest personal relationship with Clinton.
For Clinton, the selection of a running mate opens a new and important chapter in her political life.
Her first presidential campaign ended long before any serious consideration of a running mate began, so this phase of her campaign is uncharted terrain, a moment where she can choose her own partner.
She was deeply involved in the selection of Al Gore to be her husband's running mate in 1992, but this choice is hers. Her husband favors Kaine, people close to him say, but one added this week: "He gets a say, but doesn't have a vote on this."
The weekend debut of the Democratic ticket is designed to build anticipation for the party's convention starting Monday in Philadelphia. After they are formally nominated, Clinton and her new running mate are expected to embark on a bus tour to key campaign battlegrounds, similar to the "First 1,000 Miles" caravan in 1992 that took the Clintons and Gores to eight states on their way to winning the White House in November.
For her part, Clinton has intentionally not informed anyone who has gone through the vetting process of her final decision, Democrats close to the process said, in hopes of keeping her choice a secret until the last possible moment.
Booker, who often fires up audiences for Clinton, appeared with other Democrats in Cleveland on Thursday to push back against Trump and Republicans, who have spent the week assailing her character.
"I don't know who the nominee is," Booker told CNN's Jake Tapper Thursday. "The good thing about it is she has tremendous choices."
But two Democrats close to Sen. Elizabeth Warren of Massachusetts and one close to Sen. Sherrod Brown of Ohio, both of whom were on Clinton's list of contenders, said Thursday they were all but certain they had not been selected.
Warren told Stephen Colbert on CBS' "Late Show" that she thought "if it were me, I would know it by now."
All the finalists have met with Clinton at different times, Democrats close to the process say, including Perez, Booker and Warren during one-on-one meetings last Friday at Clinton's home in Washington. But this week, the Clinton campaign had a meeting with top Warren aides, trying to work out a surrogate schedule for her for the rest of the summer and fall, leading Warren's team to believe she had not been chosen.
The selection of either Brown, Warren or Booker would influence the balance of power in the Senate. Their replacement would be named, at least initially, by a Republican governor in their state, and Clinton is intent on trying to win a Democratic majority in the Senate.
Clinton started this process before her primary fight with Bernie Sanders ended with what aides described as a "fluid" list, including several potential running mates. Several were eliminated, including Colorado Gov. John Hickenlooper, Housing and Urban Development Secretary Julian Castro and James Stravidis, the former supreme allied commander of NATO and a retired four-star Navy admiral.