WASHINGTON - US Senator Tim Kaine is Hillary Clinton’s pick to be her running mate on the Democratic Party’s ticket for the White House, the presumptive Democratic presidential nominee announced Friday.

Kaine, a former governor, has "devoted his life to fighting for others," Clinton’s announcement said.

The 58-year-old Kaine from Virginia had been the focus of increasing speculation in recent days, as Clinton insiders said that former president Bill Clinton, the presumptive nominee’s husband, was backing Kaine.

The Clinton team has been high on Kaine from the start because of his extensive governing experience — he is a former governor, lieutenant governor and Richmond mayor. Clinton’s pick reflects a calculation that she needs a candidate who will be in a strong position to govern versus a progressive firebrand to help her rev up Democratic base voters. As a member of the Armed Services and Foreign Relations committees, Kaine would add to the Democratic ticket's national security credentials given Clinton's tenure as secretary of state.

The pick was believed to have been made earlier in the day Friday, but it was delayed after reports of a mass shooting in Munich that claimed at least nine lives.

Clinton and Kaine will campaign together for the first time in an appearance in Miami after making solo appearances in Orlando and Tampa on Friday. The Florida events come ahead of the Democratic National Convention, which kicks off Monday in Philadelphia.

The presumptive Democratic nominee had weighed whether she needed a more outspoken liberal on her ticket to satisfy the Bernie Sanders wing of the party. Yet with polls showing Sanders voters moving toward her and given Republican Donald Trump's pick of Indiana Govrnor Mike Pence, a strong conservative, as his running mate, strategists say Clinton had more freedom to pick a conventional swing state candidate such as Kaine.

The choice signals a tactical decision to make a strong play for independent and moderate voters, said Matt Bennett, senior vice president at Third Way, a centrist Democrat policy group. “Conventional wisdom says presidential elections are all about base turnout,” he said in an email. “Secretary Clinton has rejected that approach, picking a sensible, swing-state centrist. She clearly believes that the way to win in a divided country and to govern in a divided Washington is by making the tent bigger and appealing to common interests.”