Kaine in Miami: 'Bienvenidos a todos(Clinton, Kaine hit the stage for the first time in Miami )

Miami (CNN)Tim Kaine took the stage alongside Hillary Clinton in Miami Saturday and offered his first greeting to voters as a vice presidential nominee -- in Spanish.

"Bienvenidos a todos," the Virginia senator said, a phrase that translates to "welcome to everyone."

Clinton and Kaine's first joint appearance as running mates at a campaign rally here marked the official unveiling of the Democratic ticket. The duo will face off against Republican presidential nominee Donald Trump and his running mate, Indiana Gov. Mike Pence.

Right off the bat, the contrast that the Clinton campaign will seek to highlight between Kaine and the Republican ticket during the general election was clear

 Clinton introduced Kaine as someone who has shown a "lifelong commitment to social justice."

"Sen. Tim Kaine is everything Donald Trump and Mike Pence are not," Clinton said. "He is qualified to step into this job and lead on Day 1. And he is a progressive who likes to get things done."

Her introduction of Kaine was in stark contrast to Trump's first event with Pence last weekend. Trump took the stage by himself and spoke at length before turning to the topic of his new running mate. Trump and Pence, who did not know each other prior to this election, also lacked the warmth and admiration that was evident between Clinton and Kaine on stage in Miami on Saturday.

She heralded her pick as a man of faith, willing to work across the aisle and committed to furthering the progressive cause.

"In both of our families, faith wasn't just something we talked about at church on Sundays, it was a call to serve others in every way that we can," she said.

As he looked on from a stool behind Clinton, Kaine lived up to his reputation of "Mr. Nice Guy," grinning and waving to the crowd, and clearly reveling in the moment.

But Clinton warned the crowd: "Make no mistake, behind that smile, Tim also has a backbone of steel."

Why Tim Kaine has already made history

Pivoting to an issue that holds personal significance for Kaine, Clinton continued: "Just ask the (National Rifle Association). Over and over again he has had the courage to stand up to the gun lobby in their own backyard."

During his tenure as governor, Virginia grappled with the 2007 Virignia Tech massacre -- the country's biggest mass shooting up until that point. Fellow Virginians to this day praise the way Kaine handled the tragedy -- an episode that they say demonstrated both compassion and governing skills.

Trump offered his thoughts on Kaine via Twitter, saying: "Tim Kaine is, and always has been, owned by the banks. Bernie supporters are outraged, was their last choice. Bernie fought for nothing!"