Not only is he leading but he’s still got that (likely) endorsement from Bob Vander Plaats coming, which will further consolidate evangelicals behind him. Ben Carson has collapsed from 32 percent two months ago to 13 percent now. How much of that remaining 13 percent will shift to Cruz once Vander Plaats weighs in?

We’re six months into the campaign and the first shot still has yet to be fired in the inevitable Trump/Cruz war. Any minute now.

No fancy math needed to see what’s happening. The romance with Carson is over and the romance with Cruz — and, to a lesser extent, Rubio — has begun, and this time it’s unlikely to be a fling. Steve King’s endorsement seems to have helped Cruz a bunch: 19 percent say it made them at least a little more likely to support him. Carson led in October among evangelicals with 36 percent, 18 points better than Trump. Now Cruz leads with 30 percent, 12 points more than Trump and 14 more than Rubio. Carson is now fourth in that group. Yikes. This isn’t the only recent poll to show movement in Iowa for Cruz either; the two most recent polls of the state each had him passing Carson for second place, and Quinnipiac had him just two points behind Trump. There’s every reason to think Monmouth has the order of the race correct right now.

Here’s a result I didn’t expect. The primaries, including and especially Trumpmania, are all about immigration, right? That’s what the media (and plenty of Trump fans) keep telling me. Makes sense too that immigration would be especially important in a state where Steve King has lots of influence. And yet here’s the list of most important issues to Iowans:

Don’t focus on this month’s numbers, which are obviously affected by the terror attacks in Paris and San Bernardino. Even in July, immigration was a fourth-place issue. That helps explain how Rubio, the great amnesty heretic, can suddenly be hot on Trump’s heels there. Apart from one outlier poll last month by Gravis, which had him at 18 percent, these are the best numbers Rubio’s posted in Iowa to date — and when you combine Iowans’ second choice with their first, he’s actually ahead of Trump, 34 percent to 33. (Cruz leads with 42 percent.) Someone’s going to win a bunch of center-right votes in Iowa, just like Romney did in 2012. Right now Rubio’s the guy.

Three questions, then. One: Is this endgame for Jeb? No one expected him to win or even contend for Iowa, but the calculus for GOP donors is different if Rubio’s got a shot at Iowa than if he doesn’t. The donor class wants to stop Trump, sure, but they’re also desperate to stop Cruz; until now, I think they viewed Iowa as a lost cause, a state that would either go to Trump, Cruz, or (in the best-case scenario) Carson. Rubio pulling off a win there would be an establishment dream scenario, though, not only stopping Cruz cold and blowing up Trump but setting Rubio on track to win New Hampshire too and maybe, against all odds, race to an easy win for the nomination. Your call, Bush donors. Keep pumping the dry well you’ve got now in hopes that something will happen before NH or go all-in for Rubio in Iowa to try to make this a short race. Two: Can Trump win New Hampshire if he loses Iowa to Cruz? I think he can, although the margins do matter. If Cruz beats Trump by two points in Iowa, the media will credit Trump the next day for defying the odds and nearly pulling off a win in a state that’s supposed to only break for social conservatives. “Trump is for real!” the headlines will read. If he loses by 15 points, the media will say that Trump is a paper tiger, the Howard Dean of the 2016 GOP primaries. New Hampshirites who are undecided in the final week will read that, tell themselves that Trump has no chance in their state, and tilt towards someone else.

Three: What will the Trump/Cruz war look like?

Will be interesting to see how @realDonaldTrump attacks Cruz. Seems opening is to attack him as a politician who doesnt get biz or winning.

— Philip Klein (@philipaklein) December 7, 2015

I think that’s right. Trump can’t hit him for being too conservative; that’s suicide in a Republican primary, no matter how heterodox Trump’s own base might be. If he’s smart, he’ll dial in on Cruz’s role in the 2013 shutdown and the economic disruption that future brinksmanship by President Cruz might bring. Trump’s blue-collar fans don’t care about government shutdowns. They like Trump because he promises to make the government work better, not to slow it down or shrink it. The X factor here is whether Trump will try to cast doubt on Cruz’s eligibility by pointing out that he was born in Canada and only recently renounced his (dual) Canadian citizenship. Trump speculated about Cruz’s eligibility back in March but then clarified in September, when Cruz was applauding everything he said, that he felt confident that Cruz was a U.S. citizen under the law. Let’s see how confident he is now that he’s in second in Iowa.

Update: A belated exit question for you. Rubio’s been working hard lately to paint Ted Cruz as dangerously irresponsible on national security thanks to his vote for the USA Freedom Act. Meanwhile, terrorism and national security are among the most important issues to Iowans — and yet it’s Cruz who now leads there. Is that evidence that Rubio’s attacks haven’t gotten a lot of attention yet or that they’re simply not working?