ARI SHAPIRO, HOST:
Donald Trump will meet privately tomorrow with Republican leaders in Congress. Since Trump locked up the party's presidential nomination last week, most of those leaders have endorsed him, with one notable exception - House Speaker Paul Ryan. Ryan says by withholding his support for now, he will help unite a divided party. NPR congress reporter Susan Davis starts us off.
SUSAN DAVIS, BYLINE: The speaker's shock announcement that he wasn't quite ready to rally behind Trump just yet has chaffed some of the New York businessman's leading allies on Capitol Hill, like Alabama Republican Sen. Jeff Sessions, who says he's disappointed in Ryan.
JEFF SESSIONS: Frankly, yes, I think he made a mistake on that. I'm not sure what was in his mind, but I think that can be repaired.
DAVIS: Sessions says one way is for Ryan to accept the fact that voters sifted through 17 Republican presidential candidates, and Trump won out.
SESSIONS: A number of candidates took on Speaker Ryan's position, and they're no longer heard of. They have disappeared off the race.
DAVIS: So he says it's not Trump who has to change; it's Ryan.
SESSIONS: Trump is not going to change his fundamental campaign themes. he believes in what he says, and the people have ratified it.
DAVIS: The two men have sharp disagreement over taxes, trade, immigration and foreign policy. Ryan says he's not necessarily trying to change Trump's position on those issues. The Republican Party is big enough for both of their worldviews.
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PAUL RYAN: This is a big-tent party. There is plenty of room for different policy disputes in this party. We come from different wings of the party. The goal here is to unify the various wings of the party around common principles so we can go forward unified.
DAVIS: House Republicans are generally supportive of the speaker's slow-walk to embracing Trump's nomination, but that's most believe it's only a matter of time before he does.
CHRIS COLLINS: I believe Speaker Ryan will be supporting, with enthusiasm, Mr. Trump.
DAVIS: That's New York Republican Chris Collins. He was the first Republican to endorse Trump back in February. Collins is trying to rally the Trump and Ryan wings of the party and figure out how they can run together in the general election.
COLLINS: And members I know talking to me - what's the message? I say it's simple - secure our borders, bring our jobs back and keep our country safe, defeat ISIS. They're like, all right, I can go sell that.
DAVIS: Ryan holding back his endorsement provides cover for other reluctant Republicans to do the same, like Pennsylvania Republican Charlie Dent.
CHARLIE DENT: You know, he expressed what many of us feel - that, you know, we're not prepared to endorse Donald Trump at this time.
DAVIS: Not at this time. But most House Republicans, like Oklahoma's Tom Cole, are coming around to this general-election reality.
TOM COLE: Most of my voters are going to end up voting for Donald Trump. And so I'm going to be on the same ticket with him.
DAVIS: Cole says he's confident he'll agree with Trump on more issues than he does likely Democratic nominee Hillary Clinton. So he reasons...
COLE: Why do I want to be in a fight with my own top of the ticket? I don't see anything to be gained by that.
DAVIS: For Republicans like Cole, it's better to join Trump than fight him. And tomorrow, Ryan will step closer to deciding which path he will take this November. Susan Davis, NPR News, the Capitol. Transcript provided by NPR, Copyright NPR.