Appropo to an agricultural State, there are a cornucopia of reasons. Let roladex through them:
1) Iowa evangelicals didn't follow the sinfully bad example of the Apostles Huck and Santorum.
For months I've been alternately wailing, gnashing my teeth, tearing my sackcloth, and wearing ashes that so many ostensibly Christian voters (62% of the Iowa GOP electorate) could be supporting a candidate who not so much was just not one of us, but so mockingly pandered to us in such a way as to gratuitously go out of his way to flaunt it. "I've never sought God's forgiveness," "I eat my little cracker and drink my little wine," "Two Corinthians," "damn" this and "hell" that and dropping F- and S- bombs in his stump speeches and telling off-color jokes at Liberty University. I'm the first to admit that I never have been and never will be a single-issue or interest-group voter, but didn't this crapola have to rub Iowa evangelicals enough the wrong way as to make them reconsider their Trumpmania?
Indeed it did....
....and I tend to think that perhaps it was all along, and the polls simply did not reflect it. The Cruz attack ads highlighting what the Texas senator meant by the term "New York values" and the preponderance of big-time local evangelical leader endorsements for Cruz didn't hurt, either.
2) Skipping last Saturday's Fox News-moderated debate over his grudge-holding and ego snit against Megyn Kelly was a big, extended middle finger to Iowa voters.
There having been so many debates by this time, I didn't really credit this argument with much proverbial "oomph". It's difficult for us political junkies not to think that if voters haven't made up their minds after seven bleeping months and an avalanche of debate and rallies and ads and jibber-jabber, they never will. But we forget, once again, that we political junkies are the minority, and that the vast majority of Americans are apolitical and simply do not pay attention to election campaigns the same way that I don't pay attention to which Kardashian is on what cable TV show, or who's been nominated for what Oscar or Emmy or Grammy or Tony award. At least until the day before actual Election Day. For them, it's just one more thing on the to-do list on Election Eve, and not before.
Consequently, if the alleged frontrunner about which you've subliminally heard so much no-shows the final debate two days before you go to (caucus), and his two main rivals do participate and can make their final arguments for themselves unopposed and with a full room full of metaphorical media oxygen, that's going to leave a mark on the alleged frontrunner.
3) Flooding the media zone and a cult of personality flim-flammery hasn't quite replaced conventional and traditional tried & true campaign methods - in the GOP, at least.
I touched on this one last night. Ted Cruz had a vastly superior GOTV ground game and data/analytics organization that Trump, with his deep but narrow niche appeal (hence, the long-held theory about him having a comparatively low "ceiling" in a whittled-down race) couldn't overcome.
4) The polls (as I alluded to above) were just plain wrong.
This does appear to be becoming something of a trend. I've always suspected it, given (1) the media's rooting interest in seeing the GOP disrupted and perhaps irrevocably torn apart by the Trump infiltration, unwittingly on La Clinton Nostra's behalf, and (2) the uncharted territory of the Trump dynamic and corresponding absence of any polling metric to accurately measure it. In other words, how much of Trump's alleged frontrunning was real and how much of it was raging hype, celebrity saturation, and universal name-recognition? Last night we got our answer: actual results that were ten points out of phase from what the polls were purporting to tell us. And that doesn't include Rubio's surge at the finish that almost dropped Trump to third place. All of which makes all the bragging and boasting that The Donald has done about polls, practically justifying his candidacy on them, all the more deliciously ironic.
5) Bigger turnout didn't help Trump.
This is the one that should have the billionaire slumlord and his Trumplican minions pissing themselves. The basic assumption of Trump's inevitability was that he was the "populist" champion who would not so much draw in hordes of new voters as persuade hordes of disaffected and disgruntled and alienated voters back into the electoral fold, doing an "end-run" around the "establishment". Well, whether the sixty thousand additional Republican voters over 2012 were new or returning, they did show up last night....and most of them broke for Marco Rubio over Trump. How much of that was Iowa-specific (i.e. Trump boycotting the Fox debate) we'll find out a week from now, but it is not a good omen for Trumplicans.
6) Trump has become the GOP "establishment" candidate.
Sounds counterintuitive, doesn't it? But it makes sense when you stop and think about it. (1) To the degree that Donald Trump has ever been a Republican, it's most definitely been of the Nelson Rockefeller, not William F. Buckley, variety; and (2) remember how in just the past week or two The Donald went out of his way to brag about how politically correct he can be, and how the "GOP establishment" started lining up behind him - a sly bit of reverse-psychological strategic electioneering on their part, perhaps? - and his boasting about his great relationships with Harry (G)Reid, Nancy Pelosi, and Chucky Schumer and how he looked forward to "making deals" with them, pointedly omitting any mention of Paul Ryan or Mitch McConnell in that context. It struck me as the overconfidence of a con artist who takes his foot off the proverbial gas, believing his marks are already skinned when they're not. In Iowa they weren't, they listened, and he paid for it. And this perception might be very difficult of Trump to shake.
7) Trump has lost GOP voters on the economy and national security.
That's what the Iowa "entrance polls" indicated. Trump trailed Rubio by six points on the former, and Cruz by nine points on the latter. Polls had shown him leading amply on both. And even on immigration, he was only ten points ahead of Cruz.
What all of this seems to come down to is that, as Dr. Krauthammer told Megyn Kelly last night, the hype bubble has been punctured. Trump isn't invincible or inevitable after all. He hasn't "reinvented" politics, much less taken it over by the overpowering aura of his testicular manly swagger. The "professional politicians" are still in the game, and last night in Iowa, they came through - as did Iowa GOP voters.
That's not to say that Trump is in any way finished. He's still ahead by enough (twenty-two points in New Hampshire, sixteen points in South Carolina, both per the RCP average) that the factors that turned a close Iowa race against him can be absorbed there. What it does mean is that both of those State's primaries are likely to be a lot closer, and above all that there will be no "table-running" Trump blitzkrieg, but rather a long, hard slog, with more, perhaps many more, losses in the offing, especially as the campaign heads into the Cruz-centric "SEC primaries". Does the man who has built his entire reputation and image on never losing have the, well, testicular fortitude to endure that?
Perhaps this is a Freudian clue:
Really, Donnie? After a single defeat? And you're already slamming the voters with only forty-nine more States to go?
I report, you decide.....
UPDATE: Trump picks up the highly-sought-after, deeply coveted....Scott Brown endorsement.
Erick Erickson covered this one nicely: