The 125,000 red, white and blue balloons have dropped and are deflating in unceremonious heaps on the ground as the Republicans wrapped up their convention in Cleveland, and Hillary Clinton is set at any moment to announce her pick for vice president.

The list of possible candidates, once a lengthy roster of Washington’s rising stars, has been clipped and culled to a safe handful: Virginia Sen. Tim Kaine, Labor Secretary Tom Perez, Agriculture Secretary Tom Vilsack, and Ohio Sen. Sherrod Brown.

There is, of course, the possibility of someone completely out of left field that no one is discussing, such as Colorado Gov. John Hickenlooper. Aides, clearly enjoying the speculation, not-so-subtly asked reporters when the last time Clinton did something as unexpected as that.

Clinton aides were preparing for an announcement on her social media platforms, with a weekend rally in Florida to formally introduce the Democratic ticket to the cameras. Clinton was set to arrive in Florida on Friday and stay through Saturday. Her nominating convention begins on Monday in Philadelphia.

At the campaign’s Brooklyn headquarters, the top women and men of Clinton’s tech-savvy team were essentially in seclusion, lest someone walk by their cubicles and see a draft of a tweet, video or branding. Those on the outside have taken to calling everyone who could possibly be joining the campaign “Vice President.”

While Republicans met in Cleveland, Clinton and her top advisers were going through the list in tremendous detail. As is so often the case with Clinton, she wanted every piece of information and data to review. Ever the perfectionist, Clinton did not want to go with her gut on this one and was still asking around about her options—including a phone call with President Obama. Although several outside advisers thought they could read between the lines of her thinking, Clinton is a pro when it comes to keeping her cards close and holding outsiders at arm’s length.

Kaine is seen as the leading contender, and he was doing little to conceal the fact he was in talks. He interviewed for the gig in 2008, for Obama, but was passed over for veteran Sen. Joe Biden. Now, with eight years’ more experience and a turn as the Democratic National Committee chairman, he’s a more seasoned match for Clinton. The two have a friendly relationship, and Clinton pal and Gov. McAuliffe is a booster. (Should Kaine win the vice presidency, McAuliffe would get to pick his replacement in a Senate, which could return to Democratic control if the party rides an anti-Republican wave.)

Others, though, have an appeal. Perez and Clinton have a shared appreciation for what government can—and should—do to help its citizens. Vilsack, a former Iowa Governor who is the only member of Obama’s Cabinet to have been there since Day One, was an early Clinton backer in 2008 and has similar love for nitty-gritty details about obscure programs. And Brown could help Clinton score a win in Ohio, a state that has a history for picking Presidents. (The last Democrat to win the White House without Ohio was Kennedy in 1960, and no Republican has ever done it.)

There were plenty of reasons to knock each potential pick. Kaine’s Catholicism and personal views on abortion could dog him, though he has always supported the right to have one. Perez’s activist instincts could push the pragmatic Clinton faster than she likes. Vilsack is mild at best, and his 2008 campaign against Clinton was barely a fizzle. Brown’s replacement in the Senate would be chosen by Ohio Gov. John Kasich, a Republican.

Progressives seemed destined to be disappointed. Sen. Elizabeth Warren was nowhere in the mix, Bernie Sanders is relegated to Clinton’s sidelines and others, such as Ohio Rep. Tim Ryan or New Jersey Sen. Cory Booker, were never really in the running. Housing Secretary Julian Castro, a rising star in the party, has not impressed Clinton’s team. Brown’s chances might have been doomed by Kasich.

Kaine, meantime has been blacklisted by the progressives who backed Bernie Sanders: the Virginia Senator signed letters this week calling for lighter regulation of smaller and regional banks. Democracy for America, a grassroots group that endorsed Sanders, circulated a statement saying the Kaine-signed letter “should be disqualifying.”

The very senior Clinton aides were typically mum on the pick. As with most things in the Clinton campaign, only a handful of aides and advisers knew the boss’ true thinking. As one top lieutenant put it: Those who are talking don’t know, and those who know aren’t talking.

In conversations with outside allies, Clinton has stressed that her running mate would be someone who could sit in the leather chairs in the White House Situation Room on Day One. Having spent four years watching President Obama lead discussions with his national security team, Clinton is keenly aware of the intense pressures in that basement hive of conference rooms. She wants someone who can do it with a minimal learning curve.

If Clinton nominates a Senator for the ticket, she may hurt Democrats’ chances of retaking control of the Senate next year. Though McAuliffe would appoint a temporary replacement to fill Kaine’s seat, the commonwealth would hold a special election in November 2017 for a full-term replacement; Clinton’s advisers fear Virginians could elect a Republican in an off-year race. Warren, though she is not likely to be the nominee, would also be replaced by a Republican governor, Charlie Baker. Clinton and her advisers see a Democratic Senate as essential for her legislative agenda.

Clinton aides also are sensitive to her worry that some voters might end up pining for the top of the ticket to be swapped. At no point, one adviser said, does Clinton ever want to turn on the television to see an Ohio voter tell a reporter that he voted for the Democrats, but, man, he wishes the VP nominee were the presidential contender. Clinton has insisted that no running mate will outshine her.

But when Clinton makes her choice known in the next few days, there’s no way the second name on the ticket can dodge overshadowing her, at least for a day.

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Write to Philip Elliott at philip.elliott@time.com.