Hillary Clinton’s vice presidential running mate, Sen. Tim Kaine, made his first campaign appearance Saturday at a rally in Miami.

Clinton announced Kaine as her vice presidential pick on Friday night after a monthslong search. The presumptive Democratic presidential nominee introduced Kaine as a progressive who likes to get things done, and said he's "everything Donald Trump and Mike Pence are not."

Describing Kaine as having a "backbone of steel," Clinton said the senator has fought for voting rights, criminal justice reform, gun control, immigration legislation and LGBT equality.

"He fights for the people he represents, and he delivers real results," Clinton said.

After taking center stage, Kaine wasted no time in his attacks on Clinton's rival, criticizing Trump's recent suggestion that he might not honor U.S. security commitments to NATO in Europe, and the real estate mogul's history of casino bankruptcies and founding the failed Trump University.

"When Donald Trump says he has your back, you better watch out," Kaine said, with Clinton sitting at his side nodding. "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."

Admitting to the enthusiastic crowd at the Florida International University Panther Arena that he understood many had probably never heard him speak before — or had possibly never even heard of him — Kaine also told supporters about himself and how he came to work in politics.

Before Kaine became a senator of Virginia, he served as governor of the state as well as mayor of Richmond and chairman of the Democratic National Committee. He has also worked as a civil rights lawyer and teacher.

The 58-year-old Kaine spoke of his life growing up in Kansas City, Missouri, and explained how he became fluent in Spanish, working as a missionary in Honduras. He said in Honduras he learned the values "Fe, familia, y trabajo" -- faith, family, and work. He spoke to the crowd in Spanish multiple times throughout his speech.

Kaine then turned his attention to Clinton and her presidential platform, touching on gun control and equal pay for women, among other issues.

"They don't come any tougher or any more compassionate than Hillary Clinton," Kaine said.

The senator wrapped up his speech by asking the crowd three questions: 

1. "Do you want a 'you're-hired or you're-fired' president?" Playing off Trump's "The Apprentice" catch phrase, Kaine led the audience into an obvious answer, saying Trump was a "you're fired" president who would lose jobs for Americans.

2. "Do you want a trash talking president or a bridge building president?" The senator said that while Trump has trashed talked multiple groups in the country, including people with disabilities and the Hispanic community, Clinton is the type of leader who builds people up.

3. "Do you want a me-first or a kids- and families-first president?" Again taking aim at Trump, Kaine argued that the businessman is the type of person to put himself before his country and that America needs a president who will put others first, like Clinton.

The appearance comes just days ahead of the Democratic National Convention, where Clinton is expected to be officially nominated as the party's presidential candidate. The DNC runs July 25 to 28 at the Wells Fargo Center in Philadelphia, Pennsylvania.