Donald Trump speaks at a campaign rally at the University of Iowa in Iowa City on Tuesday. (Scott Morgan/Reuters)

Donald Trump’s announcement that he will boycott Thursday’s Fox News debate is a major strategic blunder — the first of his otherwise brilliant presidential campaign. If he follows through on his threat, he could regret it.

First, skipping the debate makes Trump look weak. Trump’s campaign is centered on his image as the toughest candidate out there, Republican or Democrat — the man who can face down China, Iran and the Islamic State. He takes pride in throwing hecklers out of his campaign events. In October, a few months after Black Lives Matter protesters took the microphone from Sen. Bernie Sanders (I-Vt.) at a campaign rally, Trump mocked Sanders mercilessly and said it “showed such weakness.” He even put up a Web ad that asked how Sanders could fight the Islamic State if he could not handle Black Lives Matter protesters.

Well, how can Trump fight the Islamic State if he can’t handle a few tough questions from Megyn Kelly? If Trump does not show up, he won’t look tough — he’ll look like a big baby. He’ll look as though he is running from a fight. And running from a fight is not a New York value.

Second, he’s handing the stage to Sen. Ted Cruz (R-Tex.). If Trump was the front-runner with a wide lead over Cruz, that might not be a big deal. But Trump only recently regained the lead over Cruz in Iowa and is ahead by just two points, which means the two candidates are statistically tied. Giving your opponent free airtime in which to attack you without response is dumb in any circumstance — but in a neck-and-neck race like this it is political malpractice.

In the last debate, Trump did very well against Cruz, skillfully parrying Cruz’s attack on Trump’s “New York values” by wrapping himself in the mantle of 9/11. But this time Trump won’t be on the stage to deliver his rebuttal. Cruz is running very effective ads in Iowa showing Trump calling Iowa voters “stupid,” declaring Hillary Clinton “a terrific woman” and saying “I lived in New York City, in Manhattan, all my life so my views are a little bit different than if I lived in Iowa.” Cruz will level these attacks in Thursday’s debate whether or not Trump is there to respond.

Third, not showing up risks insulting Iowa voters. No doubt Trump’s hard-core supporters will applaud his decision to skip the debate, but undecided or persuadable voters might not see it that way. And there are a lot of them. A new Quinnipiac poll shows that about 4 out of 10 Iowa voters say they could still change their minds about which candidate to support. The Fox News debate will help them make up their minds. The debate is in Iowa, which means a significant number of voters Trump needs will actually be in the debate hall to assess the candidates in person. These Iowans, and those watching on TV, may not appreciate Trump’s refusal to show up or answer questions a few days before they vote.

There is a lot at stake for Trump. If he wins Iowa and then goes on to win New Hampshire (where he has a commanding 20-point lead over the rest of the field), it is hard to see how he loses the GOP nomination. This move could cost him that crucial first victory in Iowa.

Perhaps Trump’s decision won’t hurt him, and he’ll win Iowa all the same. Or perhaps Trump will still show up, as he has the last three times he toyed with skipping a debate. If he does, his “boycott” will be not a blunder, but another example of his political genius. It will mean that, once again, he has focused all attention on himself — sucking up all the oxygen in the media atmosphere with the saga of whether he is going to show up.

But if Trump does not show, and loses Iowa, he will look back at this decision as the turning point that cost him a chance to bury Cruz. As Cruz himself put it yesterday, “If Donald wins Iowa, he right now has a substantial lead in New Hampshire. If he went on to win New Hampshire as well, there’s a very good chance he could be unstoppable.”

Cruz is right. Trump has a chance to put a stranglehold on his competition in Iowa — and he’s risking it all because he is afraid of taking questions from Megyn Kelly?

Now that would be weak.

Marc Thiessen is a Fox News contributor. Read more from Thiessen’s archive, follow him on Twitter or subscribe to his updates on Facebook.