 -- Hillary Clinton has chosen Virginia Sen. Tim Kaine, a man she called a "relentless optimist" who "devoted his life to fighting for others,” as her running mate.

Clinton announced her choice in a text message (in English and in Spanish) sent to supporters: “I’m thrilled to tell you this first: I’ve chosen Sen. Tim Kaine as my running mate."

The presumptive Democratic nominee also tweeted out her running mate decision.

Kaine tweeted he's "honored" to be Clinton's VP. Clinton and Kaine's first appearance together as a Democratic ticket will be tomorrow at a campaign rally in Miami, Florida.

Kaine has long been considered to be at the top of Clinton’s short list. He was previously vetted for the vice presidency by Barack Obama in 2008. Kaine was an early supporter of Clinton’s, appearing at a “Ready for Hillary” breakfast in May 2014 where he urged her to enter the 2016 presidential race.

Before tonight’s announcement, Kaine last appeared on the campaign trail with Clinton at a stop in Annandale, Virginia, on July 14. During that appearance, Kaine appeared to be auditioning to be Clinton’s running mate. He utilized his fluent Spanish to explain why he was “listo” or ready for Hillary.

“We were ready for Hillary because Hillary's ready for us. Hillary's ready for Virginia. Hillary's ready to be president. Hillary's ready to be our leader. Hillary's ready to make history. And that's why we're ready for Hillary," Kaine said at the time.

While Kaine has acted as a surrogate for Clinton, the two have not appeared at a campaign stop together. Today’s announcement marked their first joint campaign appearance.

Kaine told NBC in June that he “encouraged her to run in May of 2014, because I could telescope forward and see some of the challenges that this nation would be facing. And I decided that by reason of character, by reason of background, and experience, but also especially by reason of results, she would be the most qualified person to be president in January of 2017.”

Pundits have described Virginia as a pivotal battleground state in the 2016 race, and Kaine will help in the efforts to deliver the state to the Democrats.

Prior to being elected to the Senate, Kaine served as governor and lieutenant governor of Virginia. In 2009, President Obama picked Kaine to lead the Democratic National Committee.

Kaine, a devout Catholic, is married to Anne Holton and has three children. His father-in-law was the governor of Virginia from 1970 to 1974 and is a political mentor to Kaine.

The Clinton campaign can also utilize Kaine’s fluency in Spanish to appeal to Latino voters. Kaine mastered the language when he took a year off from Harvard Law school to work as a missionary in Honduras. Kaine has described that experience as cementing his commitment to serve others.