By Byron York

NEA Columnist

WEST DES MOINES, Iowa -- Donald Trump's supporters showed up at the Sheraton Monday night fully expecting their man to win the Iowa caucuses. And why shouldn't they? Trump had held a lead of varying sizes in 13 of the last 13 polls listed in the RealClearPolitics average of Iowa polls. How could that not win?

Months ago, before Trump took the lead in Iowa, a number of analysts argued that he wasn't a "good fit" for the state's Republican electorate, made up heavily of voters who describe themselves as born-again evangelical Christians. Then Trump took the lead and -- in the polls at least -- fought off challenges from Ben Carson and eventual winner Ted Cruz. So analysts thought Trump might not be so bad a fit after all.

But on caucus night, some of Trump's supporters returned to the old "bad fit" theory to explain Trump's surprise loss.

"It was the evangelicals," said Dick Stoffer of West Des Moines. "They've done it before -- they did it four years before with Santorum, they did it with Huckabee before that."

"The evangelicals," said Carol Anne Tracy of West Des Moines. "We've got a lot of evangelicals, and I just don't think they felt that (Trump) praised God enough."

"It's happened before -- the guy with the biggest Bible wins Iowa," said Ken Crow, a Tea Party activist from Winterset.

The caucus results -- Trump soundly beaten by Cruz, finishing barely ahead of Marco Rubio -- seemed to confirm another nagging suspicion about the Trump campaign: that it had not paid sufficient attention to turning out its voters.

Most of the people at the Trump event had attended caucuses earlier in the evening. At those caucuses, the presiding officer asked whether there was a representative from each campaign present to speak, and, if not, whether anyone attending would like to speak on a particular candidate's behalf. At the caucus I attended, in Pleasant Hill, a suburb just east of Des Moines, there was no one to speak for Trump -- no representative of the campaign -- and no voter willing to stand up and speak on his behalf. (The precinct ended in a Cruz landslide: 110 votes for the Texas senator, versus 36 for Trump and 34 for Rubio.)

At the Sheraton, some Trump supporters had similar stories.

"We were at a caucus and Trump didn't even have anyone there to speak for him," one man told me.

"That's insane," added a man nearby.

"I was at a caucus, and no one spoke for him there, either," added someone else.

I asked everyone I talked to at the Sheraton whether they felt Trump had made any mistakes in the campaign, like deciding not to attend last Thursday's Republican debate. Most felt Trump had made the right call; they weren't in the mood to second-guess their candidate. But in light of the caucus results, the debate decision looms as a critical error in judgment for Trump.

In the days leading up to the voting, when I talked to voters on the fence between candidates -- people who could possibly be persuaded to support Trump -- one thing became clear: everybody watched the debate. It was the only debate held in Iowa, and it took place in the final days of the campaign, when voters who had been reluctant to pay attention months earlier had finally become interested and involved. They all tuned in. And Trump wasn't there.

"That was the one thing that I thought was a clear mistake," Republican blogger Craig Robinson, a former political director of the state GOP, said in a phone conversation Monday afternoon. With that one decision, Trump undermined a lot of the work he had done in the previous months.

The debate decision showed that Trump's political instincts could be wrong. But the caucus loss could point to even more serious problems ahead for Trump.

A lot of people like Trump and agree with what he has to say. They cheer him on. But as the time to vote approaches, they apply a seriousness test, a test of whether they would trust him in a position of grave responsibility. The difference between Trump's high pre-caucus polls and his underwhelming support in the actual caucus could indicate that voters who had supported him for months beforehand began to develop doubts as the time neared to actually cast a ballot. Would it be safe and smart to vote for this guy?

Just as fundamentally, Trump's Iowa loss could cast doubt on his unconventional tactics in other states. Trump's strategy is based on a big bet: that because voters are tired of conventional politicians, then they will also be resistant to conventional political appeals. Iowa proved just the opposite. Ted Cruz won a smashing victory by doing things the old-fashioned way, visiting all of Iowa's 99 counties, pressing the flesh in gatherings of 100, 150 people, and tailoring his pitch to appeal to concerned evangelicals. That -- plus a highly sophisticated data operation -- won the day for Cruz. Trump tried something different, and it didn't work.

So Trump now heads to New Hampshire, where, unlike Iowa, his lead in the polls is enormous -- more than 20 points. Will that lead go away on election day, too?

Trump's first encounter with the voters should probably teach him several things. One, never suggest that you've got their support in the bag. Two, show up at the biggest events. And three, do everything you can to turn out your voters.

All that will be important. But even more critical will be questions about Trump's judgment and temperament. If Iowans who once supported him did in fact retreat when it came time to enter the voting booth -- if they did in fact worry that he is just not serious enough to become president -- Trump has a problem that might not be possible to solve.