Tim Kaine, the former governor of Virginia and current U.S. Senator, was introduced for the first time by the Democratic presumptive nominee at a rally in Miami, with Clinton saying that Kaine was everything their Republican rivals Donald Trump and Mike Pence were not.
The selection of Kaine, a self-described "boring" Virginian with a reputation for low-key competence, could appeal to independents and moderates, but it quickly angered liberal groups that object to his advocacy for an Asian free-trade pact.
The Spanish-speaking former Virginia governor and Richmond mayor fit Clinton's long-stated criteria that the vice presidential choice be a capable and reliable partner who is ready to take over the presidency if necessary.
Clinton made the announcement via Twitter and a text message to supporters after the first day of a two-day campaign swing in Florida. She called Kaine to tell him about 40 minutes before the announcement, and called President Barack Obama shortly after Kaine.