MICHEL MARTIN, HOST:

Now it's time for our feature Word You'll Hear. That's where we try to understand what's happening in the news by parsing some of the words associated with them. Here's a hint about today's word.

(SOUNDBITE OF TV SHOW, "VEEP")

JULIA LOUIS-DREYFUS: (As Selina Meyer) Would you please hang up the phone because I'm the [expletive] vice president of the United States, and I have something to say.

MARTIN: That, of course, is Julia Louis-Dreyfus from the TV show "Veep." And that's this week's word as in vice president. And we know it's not really a word, but we're going with it because there's just a week to go until the nominating conventions for the major political parties start. And if history is any guide, we should hear Donald Trump and Hillary Clinton announcing their running mates soon.

NPR national political correspondent Mara Liasson is watching all of this, so she's going to tell us more. Hi, Mara.

MARA LIASSON, BYLINE: Hi, Michel.

MARTIN: So I know we always ask this, but I still have to ask this. Has it ever really made a difference whom they pick?

LIASSON: It's a really good question because it's been a very long time since a vice presidential pick delivered his own home state, like Lyndon Johnson did for John Kennedy. Generally, they don't. But they can harm your ticket. You could argue that Sarah Palin hurt John McCain.

So overall you don't want to do any harm. And the most important thing is you want somebody ready to be president. There are other considerations. Sometimes a vice presidential pick can reinforce your brand the way Bill Clinton did with Al Gore, another young centrist Democrat from a border state. Sometimes they can help you with a wing of the party or a certain demographic.

MARTIN: So what do we know about who is on each person's list?

LIASSON: Well, on Trump's list, we know because some of the people have been campaigning with him like a reality show tryout. Mike Pence has done it. He's popular with Christian conservatives. Chris Christie the governor of New Jersey will be with him this week. Newt Gingrich former House speaker, but also an insurgent in his own way, has campaigned with him. He would reinforce Trump's brand. It would be an Al Gore-type choice.

And then there's retired Lieutenant General Michael Flynn, who Trump has talked about. But today on ABC, he revealed himself to be pro-choice and immediately the pro-life group said he should not be picked as vice president. It is, however, a time-tested tradition for outsider candidates like Trump to choose a military figure. Ross Perot chose Admiral Stockdale and George Wallace chose Curtis LeMay.

MARTIN: Well, what about Hillary Clinton? Who is she looking at?

LIASSON: Tim Kaine, the senator from Virginia, former governor, is at the top of her list. He comes from an important swing state that she needs. He also speaks fluent Spanish and has been chairman of the Democratic Party. Elizabeth Warren would help her with progressives. Sherrod Brown would help her in the Rust Belt, which is an area where Trump is very strong. But Warren and Brown share a deficit which is they come from states with Republican governors. If they won, they would presumably be replaced by Republican senators.

MARTIN: So before we go, any sense of the timing of these announcements? You know, normally, you hear about these at the nominating convention or just before. Do we expect that pattern to hold or do you think there'll be something different this year?

LIASSON: I suspect that pattern to hold. We only have a week to go before Cleveland, so Trump will probably reveal his VP pick in about a week. Hillary has an extra week, but she might want to try and steal some of Trump's thunder and announce her choice right at the end of the Republican convention.

MARTIN: That's Mara Liasson, NPR's national political correspondent. Thanks, Mara.

LIASSON: Thank you. Transcript provided by NPR, Copyright NPR.