ROBERT SIEGEL, HOST:
There's a lot of talk today about who will be Donald Trump's running mate, and Trump promises to put an end to all the speculation tomorrow. Meanwhile, the presumptive Democratic nominee is campaigning with the man rumored to be her top choice. Hillary Clinton hit the trail with Virginia Senator Tim Kaine. They were in Annandale, Va., this afternoon, and that is where NPR's Tamara Keith joins us from now. Hi, Tam.
TAMARA KEITH, BYLINE: Hi, Robert.
SIEGEL: What did people see of Tim Kaine there today?
KEITH: First, he showed off a not-so-secret skill he has. Take a listen.
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TIM KAINE: (Speaking Spanish).
SIEGEL: Habla espanol.
KEITH: Yes, exactly. He speaks Spanish. He's a former governor of Virginia, also fluent in Spanish. And if Clinton is going to win, a key part of her coalition is going to be Latino voters. So if Kaine were to be her running mate, he could go into Latino communities and deliver whole speeches in Spanish. He also then tried out the other thing that vice presidential candidates are often called on to do, which is to be the attack dog. And he presented a series of zingers like this one.
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KAINE: But he's a you're fired guy - outsourcing jobs, stiffing contractors, being against minimum wage, being against equal pay for women, fighting with labor. He's a you're fired guy. And if you want a you're fired president, well, you've got a choice, but we're making a different choice. We want a you're hired president - a you're hired president.
SIEGEL: So a bilingual attack dog. What do we know about Clinton's vetting process for vice presidential candidates and where it stands?
KEITH: Well, what we do know is that the Clinton campaign, aside from this event with Tim Kaine, is carrying out its process in a far less public way than the Donald Trump campaign. It's a more traditional approach. Last week, Clinton met at her home for an entire day with aides and lawyers who have been building files on potential candidates. We know this not because the campaign announced it, but because there were TV crews staked out at her house in Washington, D.C.
The campaign itself is on total lockdown about the VP search. They won't confirm anything, they won't deny anything, and they are basically skillfully dodging all questions about it. Today, reporters asked Kaine and Clinton, as they were shaking hands, about this VP - the veepstakes (ph) - and they didn't acknowledge the question.
SIEGEL: Well, if Senator Kaine is so high in the veep race here, what's so attractive about him?
KEITH: Well, he's a very loyal Democrat. He ran the party for several years. And he has executive experience as governor of Virginia. Foreign policy experience in the Senate - he serves on the Armed Services Committee. So he fits the main qualification, which is being able to step in as president if needed.
Also, he won't overshadow her. He has admitted that he is a boring guy, and he is considered a safe choice, sort of a wonky guy. And (laughter) at the end of the event, Clinton finished her speech. She looked over at Tim Kaine. They smiled at each other, and they did this little fist bump.
SIEGEL: Now, besides Tim Kaine, briefly, who else is being floated as a potential running mate for Hillary Clinton?
SIEGEL: Elizabeth Warren, the Massachusetts senator and progressive icon, Tom Perez, the labor secretary - also a policy wonk like Clinton - Sherrod Brown, another progressive senator - he's from Ohio - and to a lesser extent, Tom Vilsack, the agriculture secretary. Brown and Warren would seem to be long shots, though, because they come from states with Republican governors and would then be replaced, likely, by a Republican in the Senate.
SIEGEL: That's NPR's Tamara Keith. Tam, thanks.
KEITH: You're welcome. Transcript provided by NPR, Copyright NPR.