Byron York of the Washington Examiner ponders the impact of an Iowa caucus loss for Republican presidential candidate Donald 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.

Trump also said a few things that might have crossed a line with Iowans. One was the “how stupid are the people of Iowa” line from a few months ago that was featured in a recent Cruz attack ad. The other was the late-in-the-campaign statement that he could shoot someone on Fifth Avenue and not lose voters. At a Rubio rally in Sioux City a few days before the caucuses, I met a man named Gary Swanson who told me he once seriously considered supporting Trump — until he heard the shooting quote.

“He makes the statement that he’s so popular that he could shoot a person on Fifth Avenue without losing a vote. Well, he just lost two right here when he said that,” Swanson said, pointing to a friend who had accompanied him to the Rubio event. …

… 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.