Yesterday’s Monmouth poll, which had Rubio in third place with 16 percent, was newsy because those were his best numbers in any Iowa poll since early December. Smoking-gun proof that Rubio’s on the move as late-deciders get serious! Just one problem: 16 percent was actually a point less than what he polled in the last Monmouth survey. He’d actually declined slightly over the past seven weeks. Even good news comes with bad news for Rubio these days.

Until now:

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That’s strikingly similar to Monmouth’s results, with Trump exactly seven points ahead of Cruz and Cruz exactly seven points ahead of Rubio. (In fact, the last poll of Iowa before these two also had Trump by seven over Cruz.) What’s different is the trend line for Rubio. Less than three weeks ago, the last time WSJ/NBC polled Iowa, he was at 13 percent. He’s climbed five points in that time. Trump, meanwhile, has climbed eight while Cruz has dropped three. That Trump’s support is increasing while Cruz’s has slipped a bit seems indisputable given the last few polls. What WSJ/NBC is suggesting here is that there may be another trend quietly happening — namely, Rubio building momentum as he campaigns intensively in Iowa over the final week. He’s going to go all-out to try to destroy Cruz tonight at the debate too, knowing that if he can damage Cruz enough to make Iowa a battle for second place between them rather than a battle for first between Trump and Cruz, Rubio will be exactly where he wants to be before New Hampshire. Instead of the young star who underperformed, he’ll be the “surprisingly strong” center-righty who suddenly looks primed for a long race with Trump and Cruz. It’s only one poll but it’s the best news Rubio fans have had in months.

Want more evidence that Rubio is threatening in Iowa? Well, at this point you’d think Cruz would be throwing everything he has at Trump to try to win the caucuses. But he isn’t. He just released a new ad in Iowa targeting — ta da — Marco Rubio:

Just as striking, Mr. Cruz’s campaign quietly began running an ad in Iowa Thursday targeting Mr. Rubio over his support of “amnesty” for undocumented immigrants.

Showing images of Mr. Rubio standing with the so-called Gang of Eight senators who wrote the 2013 immigration overhaul, the spot features a clip from Rush Limbaugh explaining that the Florida senator was a part of that group while Mr. Cruz was not.

The ad, which Mr. Cruz’s campaign did not release to the media, also flashes a message on screen: “Rubio betrayed our trust.”

Cruz also added a bit to his stump speech about Rubio having too quickly abandoned the fight against gay marriage after the Supreme Court legalized it. I wonder what Cruz’s internal polling is showing about Rubio making inroads with evangelicals. That’s who Cruz is counting on to deliver Iowa to him but he’s got a lot of forces trying to tug Christian voters away now — Huckabee and Santorum signaling their preference for Trump by attending his rally tonight, Rubio possibly picking up momentum in Iowa in the closing days, and even Trump’s own surprising strength among evangelical voters. Toss in the chance that Ben Carson’s supporters will stick with him instead of abandoning him for Cruz on Monday and Cruz has to worry not only about Trump bringing in independents as first-time Republican caucusgoers but about the entire field eating away at his core support.

One more piece of evidence, this time from Dave Wasserman of FiveThirtyEight in a post titled “It’s Rubio or Bust for Republicans Who Want to Win.” This isn’t evidence of Iowans tilting towards Rubio but rather of why they might — namely, that there is reason to think he’s more electable than Cruz or Trump. If Rubio can somehow make a convincing electability pitch tonight, it might do something for him:

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Based on the fact that he’s only had a couple of polls putting him within striking distance of Cruz, I would have guessed that Rubio has something like a 1-3 percent chance of winning Iowa outright. FiveThirtyEight puts his odds at 10 percent. (Trump and Cruz are now tied at 44 percent each.) Hmmmm. Iowa polling, especially in the final days before the caucuses, has been infamously volatile and now we’re getting a Fox News debate sans Trump just to add to the uncertainty of it all. I think Rubio’s still destined for third but it may be a very strong third. And really, that’s all he’s been hoping for in Iowa for weeks now.