WASHINGTON ― Hillary Clinton has picked Sen. Tim Kaine (D-Va.) to be her vice presidential running mate, tapping the popular former governor of a swing state over several more liberal picks on her short list.

I'm thrilled to announce my running mate, @TimKaine, a man who's devoted his life to fighting for others. -H pic.twitter.com/lTVyfztE5Z — Hillary Clinton (@HillaryClinton) July 23, 2016

Clinton and Kaine are set to appear together at a rally in Florida on Saturday.

The selection of Kaine, a well-liked moderate in the Senate, is likely to be seen as a sign by many on the left that Clinton is less concerned about maintaining intensity among the army of liberals who backed Sen. Bernie Sanders (I-Vt.), and more concerned about the electoral map when her opponent is Donald Trump.

President Barack Obama carried Virginia in both his elections after Democrats failed to win the state since 1964, making it a key part of his national victory strategy. Kaine, who was Obama’s first chairman of the Democratic National Committee, could help Clinton do the same.

Donald Trump’s bellicose, fear-mongering nomination convention this week likely added impetus to pick Kaine, who would add another layer of executive experience and heft to the ticket.

A campaign source said Clinton and Kaine met at her home in Washington, D.C., on Thursday after doing a campaign stop in Virginia that had been scheduled as a tryout. Clinton had been impressed with Kaine’s style on the trail, which looked very much like an event with a pair of running mates. She invited him for the meeting a day ahead of sit-downs with other potential VP nominees. Those meetings leaked to the press. Kaine’s did not.

Clinton quickly determined to meet Kaine again on Saturday for lunch with their families, including Bill Clinton, Chelsea Clinton and her husband Marc Mezvinzky, and Kaine’s wife, Anne Holton.

According to the source, Clinton’s campaign chair, John Podesta, had started the VP search back in April, bringing binders of potential running mates to her Chappaqua, New York, home in a Duane-Reade bag.

His prime advice to her was: “It needs to be someone who, whenever they walk into a room, you are glad to see them and want to have them as part of any conversation.” She felt she had that with Kaine, and kept telling aides she also had complete confidence Kaine was ready for the job.

Kaine was bound to be treated skeptically by some liberals because of his position on abortion rights ― which he personally opposes but politically supports ― and trade. However, in the immediate aftermath of his pick being announced, the abortion rights group NARAL came out with a supportive statement.

In addition, a Clinton aide told The Huffington Post that Kaine had told the former secretary of state that he would oppose President Barack Obama’s signature trade deal, the Trans-Pacific Partnership agreement, in its current form. The aide said that at some point in Kaine and Clinton’s two conversations prior to the selection ― which she made Friday night, eight days after the first meeting ― he agreed with her that a trade deal had to meet certain criteria on protecting wages and national security, and that the TPP did not.

Kaine has supported legislation known as Trade Promotion Authority, for fast-track authority, which expedites trade deals like the TPP, but in relaying his opposition to it to Clinton, he formally came out against the TPP on substantive grounds.

Kaine may help Clinton carry Virginia, but her choice could also aggravate the Elizabeth Warren wing of the Democratic Party, which sees the Virginian as a business-friendly centrist unlikely to champion their top financial reform goals. They had been pulling for Warren, Sanders or Labor Secretary Tom Perez to get the nod.

Indeed, the Progressive Change Campaign Committee zeroed in immediately on Kaine’s support for fast track, which allows a president to pass trade deals through Congress with simple majorities and no amendments.

“As we saw in Donald Trump’s speech last night, Republicans will run hard against Democrats on trade this year,” said PCCC co-founder Stephanie Taylor. “Unfortunately, since Tim Kaine voted to fast track the Trans-Pacific Partnership, Republicans now have a new opening to attack Democrats on this economic populist issue.”

Liberals also complained about Kaine in 2013 when they were trying to end the Bush tax cuts, and Kaine helped broker the eventual compromise that kept the lower rates for people with incomes up to $400,000.

Still, Kaine’s nomination could hearten civil libertarians, war opponents, people concerned about gun violence, and immigration reform advocates. He has complained often about the White House’s unilateral use of war powers, and was the first Virginia governor to oppose the death penalty. He has feuded endlessly with the National Rifle Association, which is headquartered in his state, and recently called the group a “paper tiger,” since its opposition has never been enough to defeat him. He also gave the first Senate floor speech in history to be delivered in Spanish, calling for passage of an immigration reform bill.

People who know both Kaine and Clinton saw him as a choice that would help Clinton across the board.

“He’s a tremendous asset on the ticket,” said Mo Elleithee, who runs the Georgetown Institute of Politics and Public Service, and who previously advised Kaine’s Senate campaign and Clinton’s 2008 White House run.

“If first and foremost, the vice president’s role is to be able to step in, you’re not going to find anyone better,” Elleithee said.

While some in the progressive wing look askance at a former Southern governor, suspecting a Democrat in name only, some hail Kaine as progressive in his bones.

“I can assure you as a native Virginian, this caricature doesn’t at all fit the man I’ve watched over nearly 20 years,” former MSNBC commentator Krystal Ball wrote in early July.

He’s also recently been more vocal on certain issues important for the Democratic base, including reproductive rights.

Elleithee noted that Kaine used to be called the most liberal governor in Virginia history, after doing mission work in Honduras and putting his Harvard law degree to work as a civil rights attorney.

“He’s a true progressive,” said Elleithee, who could see why Clinton was comfortable with Kaine’s campaign style.

Kaine not only knows how to connect with voters, but is able to attack an opponent without turning those voters off, winning over diverse groups in cities, suburbs and the countryside.

Elleithee recalls watching Kaine when he was running for Virginia’s lieutenant governor job in 2001, after the 9/11 attacks, and being astounded at how Kaine could launch a blistering attack on an opponent and still be liked by the audience.

“I remember one speech where he had the people eating out of his hands,” Elleithee said. “It wasn’t until later that I realized, oh, my God, he just ripped his opponent’s face off, but it didn’t feel like it.”

“He can be tough, but he does it in a way that actually draws people in,” Elleithee added.

Ultimately, Clinton seems to have made the assessment that such skills are exactly what she needs for a contest against someone like Trump.

Sam Stein contributed reporting.