This isn’t the first time he’s topped 20 percent in Iowa, but it’s the first time he’s done it in three months, a meaningful data point given that the field’s almost set now. (Kasich will formally join the race tomorrow.) Also meaningful: Walker’s the only candidate to top 20 percent in Iowa this year. Since February, the only other candidate who’s reached as high as 16 percent is Jeb Bush — and he did that only once.

Walker, who was born in Iowa, has an astounding favorable rating there among Republicans right now of 73/9. His state to lose?

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He leads as first choice and second choice, so the low 20s isn’t necessarily his ceiling. Among key groups:

Tea Party – Walker leads Trump 27% to 14% among Tea Party supporters, with Ted Cruz in coming third at 12%. Among non-supporters of the Tea Party, Walker has a nominal lead (18%), followed by Trump (11%), Bush (11%), and Carson (9%)…

Evangelicals – Evangelical voters favor Walker (17%), Trump (13%), Cruz (10%), Carson (10%), and Huckabee (9%). Non-evangelical voters prefer Walker (26%), Trump (12%), and Bush (10%).

Huckabee’s fifth(!) among evangelicals, behind two stunt candidates in Trump and Carson. Gadzooks. He’ll run hard in South Carolina and in the “SEC primary” on March 1st hoping to capitalize on his regional appeal, but if he finishes fifth in his supposed stronghold he’s done. Trump’s already probably done in Iowa thanks to his comments on faith this past weekend — they had no effect in this poll, but give the attack-ad editors in other campaigns time to work their magic — although he’s boosted his favorable rating to net positive at 47/35. Jeb Bush’s favorable rating, by comparison, is 40/42. It may be that the only real threat Walker faces in Iowa is from Ted Cruz, who’s got plenty of money to spend there and who’s poised to pick up some evangelical and tea-party votes from Trump and Carson once Iowans start getting serious about the big vote. Then again, it’s Walker who leads as voters’ second choice, not Cruz. Who’s to say he won’t pick up a greater share? The only certainty after this is that (a) Walker, with his eye on New Hampshire and South Carolina, will spend most of his time at the debates attacking Jeb Bush as stale and squishy, and (b) Cruz, with his eye on Iowa, will spend most of his time attacking Walker as inexperienced on foreign policy (national security is Iowans’ top priority per today’s data) and a shameless, calculating flip-flopper on immigration. In fact, for all the heavy breathing about including Trump at the debates, the Bush-Walker-Cruz dynamic will be far more interesting. If Walker comes off as glib and uninformed and Cruz is as impressive as everyone expects he’ll be, Iowa might tighten up quickly.

Meanwhile, the Journal wonders if Walker’s win-Iowa-at-all-costs strategy will really help him win the nomination. I’m guessing … yes, it’ll help:

Scott Walker’s aides say his path to winning the 2016 Republican presidential nomination goes through Iowa, a course that hasn’t worked for any other candidate for 15 years.

Only twice since 1976 has the Iowa caucus winner ultimately become the Republican nominee for president after a competitive primary—and not at all since George W. Bush in 2000. That spotty history, combined with Mr. Walker’s decision to adopt more conservative positions to please the state’s electorate, makes Mr. Walker’s game plan an uncertain one…

Mr. Walker is seeking to remain in the top tier of candidates by the time 11 states hold primaries next March 1. A week later comes Michigan, a large Midwestern state where the Wisconsin governor can stress his regional bona fides to Republican voters who already know his story.

It’s true that Iowa hasn’t helped select a nominee in 2000, but that’s almost meaningless. The problem in 2008 and 2012 wasn’t that Iowa’s influence had faded, it was that the evangelical electorate there went for two niche evangelical candidates in Huckabee and Santorum. They weren’t built to win a national primary is. Walker is. And he has an easy foil this time in the Bush machine to help him consolidate support among voters who might have reservations about him but who really, really don’t want another Bush as nominee. If anyone’s going to shock the world by running the table in Iowa, New Hampshire, and South Carolina, Walker is by far the best positioned to do it. And like Jeb, he’s benefiting from the Trump boomlet right now. The more undecided Iowans are paying attention to Trump, the less attention they’re paying to Cruz. Both Bush and Walker, I’m sure, would love to see Trump hang steady at 15-20 percent through Iowa and New Hampshire. He, more than anyone else, could help whittle the field down to a de facto Bush versus Walker race early.

Update: Good point by a Twitter pal about something I overlooked: This is assuredly the best poll Bobby Jindal’s had so far this year. It’s hard to see how he leapfrogs Cruz among social cons, but a few good debates could make him competitive.