Cruz’s numbers here aren’t a shock — he’s been in the high teens and low twenties for awhile — but Trump hasn’t dipped as low as 25 percent in a national poll since November and Rubio hasn’t seen a number as high as 21 percent since … ever. That makes some righty poll-watchers nervous since PPP’s credibility has been attacked in the past. Not only are they liberal, they were the subject of a famous critique of their methodology by Nate Cohn in TNR a few years ago. If you’re looking to throw out this result, which no other pollster has captured, there you go. On the other hand, RCP finds them credible enough to include them in their poll average. Nate Silver’s FiveThirtyEight site also deems PPP worthy of being rated (a B- for accuracy). I’ve been writing up their polls all primary season long, including ones that showed Trump soaring. If you accepted their other polls at face value, why start ignoring them now?

It’s true, national polls are almost totally worthless — but that never stopped Trump from crowing about them at his rallies, and after a surprising result in Iowa they can be helpful in detecting whether there really has been a change in voter sentiment that might show up next week in New Hampshire. If you believe PPP, Marcomentum is real and Trump may well be on his way down the drain.

Trump’s 25% standing reflects a 9 point drop from our last national poll, which was taken the week before Christmas. It reflects an overall decline in Trump’s popularity with GOP voters. Trump’s favorability has dropped a net 17 points, from a previous +24 standing at 58/34 to now just +7 at 48/41.Trump is particularly starting to struggle on the right- he’s dropped to 3rd place with ‘very conservative’ voters at 19% with Cruz at 34% and Rubio at 22% outpacing him with that group. He does still lead with moderates and ‘somewhat conservative’ voters to give him the overall advantage.

Rubio is the candidate with the real momentum in the race. He’s up 8 points from his 13% standing in our poll right before Christmas. Beyond that he’s seen a large spike in his favorability rating- it’s improved a net 28 points from +15 at 49/34 to +43 at 64/21. That ties him with Ben Carson as being the most broadly popular candidate on the Republican side.

Things also bode well for Rubio as the field gets smaller in the coming weeks. In a four candidate field he gets 32% to 31% for Trump, 23% for Cruz, and 8% for Bush. In a three candidate field he gets 34% to 33% for Trump and 25% for Cruz. And in head to heads he leads both Trump (52/40) and Cruz (46/40). As other candidates drop out of the race Rubio is the most likely destination of their supporters.

All of those numbers will change yet again, of course, if Trump holds on in New Hampshire, which I think he will. The table below isn’t good for him, though. Bear in mind that Cruz and Rubio are both net favorable among nearly every other candidate’s supporters, meaning that if either one of them ends up in a two-man race with Trump, they’re looking good:

Rubio also does well as the second choice of supporters of Jeb Bush and John Kasich, both of whom are likely to be out soon:

On the other hand, Cruz cleans up among fans of Ben Carson, who’s also likely to be out soon. Interestingly, Christie fans prefer Cruz to Rubio as a second choice, which may be the product of butthurt over his fade in New Hampshire or may be statistical noise due to a small subsample.

One more result for you. Here’s what happens when other candidates’ voters are forced to choose between Rubio and Cruz.

I remind you again that national polls are useless, as Cruz will/would obviously do better than these numbers in his southern strongholds, which are coming up on March 1st. (Much better if Trump’s not in the race at that point.) Don’t forget, though, that Rubio’s playing a long game, eyeing the more moderate electorates that’ll show up for winner-take-all primaries when blue-state Republicans start voting later this spring. He may outperform these numbers in those strongholds, which will be trouble for Cruz.

But that’s all too far in the future. What about New Hampshire? Rubio inched up to 15 percent there in the latest poll, his best showing in weeks, but Trump’s still at 36 percent. Even if you allow for a “Trump effect” in the polls, where Trump’s support is systematically overstated by, say, five points, Rubio still has to make up more than 15 points in the next five days. And he has to do it with basically everyone in the field not only attacking him but forging alliances to attack him:

Members of the Bush and Christie campaigns have communicated about their mutual desire to halt Mr. Rubio’s rise in the polls, according to Republican operatives familiar with the conversations.

While emails, texts and phone calls between operatives in rival campaigns are not uncommon in the tight-knit world of political strategists, the contact between senior aides in the two campaigns has drifted toward musings about what can be done to stop or at least slow Mr. Rubio, the operatives said.

In a sign of a budding alliance, the aides have, for example, exchanged news articles that raise potential areas of vulnerability for Mr. Rubio. There is no formal coordination, the operatives stressed, but rather a recognition of a shared agenda…

A division of labor seems to have taken hold. While a well-financed “super PAC” supporting Mr. Bush assails Mr. Rubio on television and in the mail (it will release a new batch of ads on Thursday), Mr. Christie has stepped up the critiques on the campaign trail.

The latest joint Bush/Christie production is to attack Rubio for being unelectable because he’s … too hardline on abortion. So Rubio’s not too establishment for a Republican primary? He’s actually … too conservative? Admittedly, any attack by Bush or Christie will seem feeble because they have the stench of death around them, but I don’t get Christie’s “boy in the bubble” takedown and I don’t see how abortion is the magic bullet that destroys Rubio’s vaunted electability. All Republican candidates will be attacked as “anti-woman,” whatever the nuances of their positions on exceptions for rape. If you want to stop Rubio, you’re best off hitting him for lacking experience — which Christie and Bush are both doing, wisely — and for his great heresy on immigration. But Jeb can’t do that because he’s knee-deep in amnesty too, and no one believes Christie when he pretends to be offended by the Gang of Eight. The dilemma for Bush, Kasich, and Christie is that, while Rubio may be establishment, he’s still less establishment than they are even with the immigration bill chained to his ankles. How do you beat him in New Hampshire from the left?