The Gallup trendlines don’t lie. That’s Newt in brown and Romney in black:

Those are national numbers, not the numbers in all-important Iowa, but sneak a peek at the latest polls there in Pollster.com’s table. From the end of November through the first week of this month, Newt was above 30 percent in three separate surveys; in the three latest polls, he’s stuck between 20 and 22 percent, making the race a toss-up between him, Romney, and Ron Paul. If Perry gets a second look over the next two weeks, which seems increasingly likely, and some Iowans come home to the native Bachmann, then we’ve got a five-way jump ball on caucus day. Madness. What happens in New Hampshire if Iowa shakes out as, say, Paul 23, Gingrich 21, Perry 18, Romney 17, Bachmann 15? Is that the political equivalent of a “push” in gambling, leaving Romney the presumptive winner in NH, or does finishing fourth detonate the idea that he’s a lock to win in the northeast?

He’s not just tanking in Gallup, either. Here’s an interesting survey flagged by Sean Trende, who wonders whether Gingrich has a glass jaw:

It proceeded by dividing respondents into three groups. One of them, a control group, watched generic, non-political commercials.

A second group, the so-called “Gingrich condition,” watched a positive Gingrich ad, a negative ad about Gingrich, a positive Perry ad, and a negative ad about Perry (you can view the different ads here).

A third group, the “Romney condition,” watched a positive Romney ad, a negative Romney ad, a positive Perry ad, and a negative Perry ad.

In the control group, 42 percent of respondents made Gingrich their top choice in the GOP primary. But in the “Gingrich condition,” support for the former speaker was only 26 percent, a drop-off of 18 points. The winner in this scenario was Romney, who numbers ticked up substantially, even though viewers didn’t see any Mitt Romney ads.

Interestingly, in the “Romney condition,” where viewers saw ads about Romney and Perry, there was little effect on Romney’s support, and Gingrich’s support increased only marginally. This suggests that most of the negative information about Romney (and Perry) truly is “priced in” at this point.

Voters simply didn’t know the bad stuff about Newt yet, but thanks to Ron Paul’s attack ads, withering criticism from prominent conservatives, and media scrutiny of Newt’s old dirty laundry, they’re getting a crash course. That’s why he’s sinking — and more importantly, because of his organizational problems and decision to (mostly) avoid criticizing his opponents, he might not be able to reverse the trend. He’s not even exerting himself terrible in Iowa, in fact: He’s airing just one ad there right now and isn’t planning to begin his final barnstorming tour of the state until December 27. According to Nate Silver’s statistical model of Iowa polling, his odds of winning IA are down to 38 percent from 70 percent just a week ago; the pessimism’s even begun to show up in his InTrade numbers, which recently were cruising at around 35 percent and now are sagging at just 18. I’m not sure tonight’s debate will help him, either. Everyone knows by now that he’s good at them, which will blunt the impact of a strong performance, and meanwhile he’ll be taking shots from everyone onstage. (Except Huntsman, of course.) He’s still got seniors solidly behind him, which is a big deal, but if they start to abandon ship I don’t know how he survives. Time for some patented Romney Mediscare tactics, perhaps.

And if you don’t think things can get worse for him, here’s Ron Paul basically calling him a chickenhawk on Fox News today. Via GOP12: