Many people feel he did cross a line in a way he hadn't even done before and also that Republicans had to speak out because they believe Trump poses a danger to the party.
Donald Trump is a candidate who divided his own party more deeply than any presidential candidate has before.
As one person said to me , Republicans know [Donald] Trump is a stain on their party.
If [Hillary] Clinton wins, history will also be made: She would be the first female U.S. president, of course, but also the only candidate in the modern era, other than George H.W. Bush, who managed to follow a two-term president of her own party.
Republicans think that [Ted] Cruz would be like Barry Goldwater. He'd lose in a landslide and pull the party down with him. They'd lose Senate and House seats.
The winner's margin of victory also matters. If it's a squeaker, that will make the lessons learned for both parties much murkier.
As one conservative intellectual said to me - he said if the choice is between [Joseph] Stalin and [Adolf] Hitler, I'd pick Stalin, meaning Ted Cruz because he's more predictable. So there's real civil war inside the Republican Party.
As those states and others in the South and West become more diverse and educated, they will become harder for the Republican Party - in its current form - to win.
Jeb Bush was supposed to be the establishment candidate, but he didn't catch on. And the extraordinary thing about this Republican primary is that the establishment, moderate wing of the party has sidelined itself. They're not coalescing around one candidate as they have in the past.
The Republican Party, right now, is a conservative populist party.
The lesson is that voters in both parties are in a very anti-establishment, populist mood. Hillary Clinton is the establishment candidate.
Well, it's possible that the new infusion of ad money against Donald Trump kept his margins in Kentucky and Louisiana down a bit. But we're also seeing something that we've never seen in 100 years, which is we are seeing the crackup of a major American political party.
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