At Saturday's campaign rally in Miami, and speaking occasionally in Spanish, Virginia Senator Tim Kaine used his first speech alongside Hillary Clinton to attack the record of Republican presidential nominee Donald Trump.

"When Donald Trump says he has your back, you better watch out," said the Harvard-trained lawyer. "He leaves a trail of broken promises and wrecked lives wherever he goes. We can't afford to let him do the same thing to our country."

Clinton announced her choice of Kaine, a former Richmond mayor and Virginia governor, as her running mate for vice president on Friday. The Democratic convention begins in Philadelphia on Monday and Clinton will be formally nominated as her party's presidential candidate.

"Senator Tim Kaine is everything Donald Trump and Mike Pence are not," Clinton said of her running mate, comparing him to their opponents in the November 8 election. "He is qualified to step into this job and lead on day one."

'I've never lost an election': Kaine

Introducing himself to the rally, Kaine described his childhood in Kansas City, where he helped his father in his metal-working shop. He also spoke of his Catholic mission to Honduras, where he helped teenagers with carpentry and welding - and learned to speak Spanish.

Kaine spoke emotionally as he recalled the 2007 shooting deaths of 32 people at Virginia Tech University, which occurred while he was governor. He called it the worst day of his life and promised to take on the National Rifle Association and fight for "common sense" gun control.

"I've never lost an election. I'm 8-0 and I promise you I'm not about to let that change," Kaine said.

Clinton is seen to have chosen Kaine to broaden her appeal to independents and moderates, but liberal groups and some supporters of her erstwhile rival, Senator Bernie Sanders, have expressed concern over Kaine's past advocacy for giving the White House fast-track authority to negotiate an Asian free-trade pact. But both the Clinton and Kaine camps have said he will oppose the accord.

"He fights for the people he represents, and he delivers real results," Clinton said. "When I say he's a progressive who likes to get things done, I mean it."

The two candidates have a common agreement on a number of issues, such as arranging for a no-fly zone over Syria as a way to limit the conflict, and gun control. Clinton wants to ban military-style guns in the US, which she calls "weapons of war." They also share common attitudes on education, health care and tax reforms.

While Clinton and Kaine are in favor of women's reproductive rights, Kaine has described himself as a "traditional Catholic," and has said he personally opposes abortion. "I've got a personal feeling about abortion, but the right role for government is to let women make their own decisions," Kaine said in a recent television interview.

The two candidates have staffers who know them both well. Kaine's Senate chief of staff, Mike Henry, was deputy campaign manager for Clinton's 2008 presidential run. Kaine's former Senate press secretary, Sarah Peck, is already working as Clinton's Virginia campaign spokeswoman.

jm/cmk (Reuters, AP)