ARI SHAPIRO, HOST:
In Wisconsin, voters are casting ballots in primary elections. We've looked at how the Republican and Democratic races are going in that state. Now to look at what it all could mean for the larger race to the White House. NPR national political correspondent Mara Liasson is back here with us once again in the studio. Hi, Mara.
MARA LIASSON, BYLINE: Hello, Ari.
SHAPIRO: Let's start with the Republicans. What are the stakes for Donald Trump in Wisconsin?
LIASSON: The stakes are very high. His opponents say this could be his Waterloo. If he wins all of Wisconsin's 42 delegates, he will only need 51 percent of the remaining delegates. If he loses, he'll need 56 percent. The results also could be somewhere in between because Wisconsin is a winner-take-some state.
They give 18 delegates to the winner, then three delegates each to the winner of each congressional district. There's a big difference between needing 51 percent and needing 56 percent, and that shows you how, this late in the contest, each state takes on more importance.
SHAPIRO: Setting aside the delegate math, if Trump loses Wisconsin, does that show that his presidential bid is losing momentum?
LIASSON: That's certainly how the Stop Trump people will explain it. Wisconsin is significant for Trump. I think if he wins there, he's all but certain to get the 1,237 delegates he needs to win on the first ballot at the convention this summer. If he loses Wisconsin, it's going to be much, much harder.
And Donald Trump is not gaining strength as the primary season grinds on. In other words, he's not getting bigger and bigger margins of victory. The opposition to him is just getting more stubborn. And he's had a rough couple of weeks. You had the head-spinning series of conflicting statements on abortion, his defense of his campaign manager, who's been charged with battery against a female reporter. Then there are new polls that show his unfavorable ratings with the general electorate are growing, particularly with key groups like women. He's had rough patches before, and he's famously said he could go out on Fifth Avenue and shoot someone...
LIASSON: ...And he wouldn't lose any voters. But now Republicans are saying it's not one single thing he's said or done - it's a cumulative effect. And Peggy Noonan, who's a former Reagan speechwriter and a conservative columnist, said all of them together form a large blob of sheer, dumb grossness.
SHAPIRO: OK (laughter) what do you see for the Republicans when you look beyond Wisconsin?
LIASSON: Well, beyond Wisconsin, the states coming up look pretty good for Donald Trump - New York, New Jersey, Pennsylvania, California. You've got a mix of moderate voters and voters who've been hit hard economically. That's why the Stop Trump people see Wisconsin as so important. It's their last good chance to stop him from getting 1,237 delegates at the convention.
SHAPIRO: All right, let's talk about the Democrats. Bernie Sanders has some momentum. He's been talking about a string of wins. Could a victory in Wisconsin tonight turn the race for him?
LIASSON: If he wins tonight, he will have won six of the last seven states, so that will give him a lot of momentum. And for Bernie Sanders, that always means a burst of money - many, many millions of dollars. Both Sanders and Clinton are already campaigning in New York State, her home state, which votes in two weeks.
If Sanders could beat her there or come very close, it would be a huge psychological blow. Still, it's going to be hard for him to overtake her delegate lead. If he wins Wisconsin, Sanders still needs 57 percent of the remaining delegates - 66 percent if you count the superdelegates - and it's hard to catch up because Democrats give out their delegates proportionally, not winner-take-all.
So he has to win the remaining states and win them big. Sanders's campaign says they're preparing for a contested convention. The Clinton campaign says that's out of the question. But in order for Sanders to convince the superdelegates to switch to him, he has to beat her so badly that she begins to look like a less-than-viable general election candidate, and he has not been able to do that yet.
SHAPIRO: NPR's Mara Liasson has been with us for the last four months covering these primaries and caucuses, and she will be with us all this evening as results come in from Wisconsin. Thanks, Mara.
LIASSON: Thank you. Transcript provided by NPR, Copyright NPR.