ROBERT SIEGEL, HOST:
Joining us with analysis of the Republicans' dilemma is NPR national political correspondent Mara Liasson. Hiya.
MARA LIASSON, BYLINE: Hi, Robert.
SIEGEL: We just heard several congressional Republicans saying it's time to unite behind Trump. Is House Speaker Paul Ryan likely to come around tomorrow or soon?
LIASSON: I don't think so. He said it's going to take some work to unify the party. He is the highest-ranking Republican in Washington, so his resistance to Trump is the most important hurdle Trump has to unifying the party. And the party, as you heard, is really seriously divided. And Ryan is standing in the middle of two camps. On the one side, you could call it the great accommodation - Republicans who think it's time to unify. Even if they have misgivings about Trump, they want to defeat Hillary Clinton. There's their number one priority. Those are people like Reince Priebus, of course, the head of the party, Trump's former opponents like Rick Perry and Bobby Jindal. You heard other voices in Sue's piece. On the other camp, you've got the never-Trump diehards - conservative activists, intellectuals, members of Congress like Sen. Ben Sasse, Sen. Lindsey Graham. They say they're putting principle before partisanship. You've also got the Bush family and Mitt Romney who will never support or endorse Trump.
SIEGEL: What has Trump actually said about unifying the party? And how important do you think it is to him that the party be united?
LIASSON: That's a good question. He said he'd like a unified party, but he's not sure it's necessary. In the past, he actually threatened Ryan, saying he would, quote, "pay a big price" for not supporting him. But he also told the Wall Street Journal last week that, quote, "this election is not about the Republican Party; it's about me." So Trump has broken all the rules so far and succeeded. It's possible he thinks he doesn't need a unified party. He lives and dies by the polls, and he could point to some recent ones that show him tied with Hillary Clinton in Pennsylvania - formerly blue state - Florida and Ohio as proof he's doing pretty well right now, even with a fractured party behind him.
SIEGEL: Well, in the past, Mara, presidential nominees have used their vice presidential picks to try to unify their parties. How's Trump doing on that front?
LIASSON: He's given us a couple of clues. He said he's narrowed his search to five or six people. He says he wants someone with legislative experience to help him govern and work with Congress. He's also said he'd consider someone who ran against him. A lot of Republicans have said, absolutely not; I don't want to be considered. But there are plenty of others who are available - Newt Gingrich, for instance, Rick Perry, Bobby Jindal, Bob Corker, who's a bona fide establishment figure. He's a senator from Tennessee.
SIEGEL: Chairmen of the foreign relations committee.
LIASSON: Yep. And he's heaped praise on Trump's recent foreign policy speech. So then there's Chris Christie, who was the first establishment figure to endorse him. Evangelical leaders, however, said that picking someone they'd feel comfortable with is really important and the only way that Trump can avoid large numbers of churchgoing evangelical voters deciding to stay home in November, but there's no indication that Trump is thinking along those lines.
SIEGEL: Let's turn to the Democrats, then, because Hillary Clinton's campaign says that it is vetting potential running mates for her. What is Clinton looking for?
LIASSON: Democrats say, first and foremost, she wants someone who can help her govern and who is ready to be president if necessary. And that's actually the number one criteria for Trump, too, and for anyone who's running for president. But for Hillary Clinton, there are a couple of categories to choose from. She's a more traditional candidate, so she comes at this choice in a more conditional way. First category - swing state senators - somebody like a Sherrod Brown from Ohio if she thinks she needs help in the Rust Belt, which is an area where Trump could be very competitive, Tim Kaine from Virginia, another big battleground state the Democrats need. Kaine also speaks fluent Spanish, which could be helpful. And then there are the two Hispanic cabinet secretaries, Julian Castro and Tom Perez if she needs help locking down the base. And then there's the progressive heroine, Elizabeth Warren, Elizabeth Warren, who has shown that she has a stomach for attacking Trump. She's been in a big Twitter battle with her. And of course, being an attack dog is a very important function of a vice presidential candidate.
SIEGEL: And two women on the ticket would really be crashing the glass ceiling.
LIASSON: Yes, would be crashing the glass ceiling, reinforcing her strengths. But also, Elizabeth Warren is beloved by the progressive wing of the party.
SIEGEL: That's NPR's Mara Liasson. Thanks, Mara.
LIASSON: Thank you. Transcript provided by NPR, Copyright NPR.