In coming months, Trump faces several hurdles
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The whimsical, charmed presidential campaign of Donald TrumpDonald John TrumpIvanka Trump pens op-ed on kindergartners learning tech Bharara, Yates tamp down expectations Mueller will bring criminal charges Overnight Cybersecurity: Equifax security employee left after breach | Lawmakers float bill to reform warrantless surveillance | Intel leaders keeping collusion probe open MORE (R) has been unpredictable. And to date, it has clearly been a roaring success.

Trump has been forced to spend very little money, living off saturation-level news coverage that even a president of the United States would envy.

But with the Iowa caucuses only about a month away, this race is about to turn deadly serious.

Here are four serious hurdles facing Trump:

1. He is likely to lose in Iowa. Trump remains able to attract large crowds, but much like NASCAR fans, some go to cheer on their favorite driver, and some go to see a spectacular crash. The Iowa caucuses are the most unique election contest in the presidential race, with the winner needing perhaps only 30,000 votes. Trump's organization in Iowa, despite being run by seasoned Iowa hand Chuck Laudner, is seriously lacking. The organization has not met its publicly stated goals and Trump drops in for only a couple hours and leaves, failing to do the retail campaigning that Iowa's 99 counties require. Contrast that with Sen. Ted Cruz (R-Texas), who has skillfully united conservatives behind his candidacy, winning the endorsement of firebrand congressman Rep. Steve King (R) from vote-rich western Iowa, as well as Bob Vander Platts, the undisputed evangelical leader of the state. Cruz has a large and growing organization and his campaign is peaking at the right time. Will Trump's fans turn out to caucus? Do they know where to go and what is required? I believe Trump will underperform in the caucuses and Cruz will be a rocket ship of momentum coming out of Iowa.

2. His invincibility is gone. A big part of the Trump campaign's ethos is invincibility, and this washes down to his supporters. Some like his celebrity, some like his wealth, some like his bluntness, some like his message on immigration and trade, but all like the fact that he is winning. Will they be with him if he's not winning? What happens when Trump is no longer the "momentum" candidate, sweeping up 80 percent of the media time? How will he handle bad polls?

3. The New Hampshire primary. New Hampshire's first-in-the-nation primary is 180 degrees different from the Iowa caucuses. The single biggest difference is the fact that independent New Hampshire voters can vote in either primary. In a non-incumbent year like 2016, this makes New Hampshire very unpredictable. We know that Trump is winning a large share of his support from moderate Republican and conservative Democrats. Will they instead vote in the Democratic primary to deliver a stunning victory for next-door neighbor Sen. Bernie Sanders (I-Vt.)? The biggest advantage Trump has in New Hampshire is that the "establishment" lane is divided four ways between former Gov. Jeb Bush (R-Fla.), Sen. Marco Rubio (R-Fla.), Gov. Chris Christie (R-N.J.) and Gov. John Kasich (R-Ohio). I think Rubio and Christie are the biggest threat to Trump, but Cruz will rise in New Hampshire after winning Iowa.

4. Campaigning after losing. We simply do not know how Trump will handle losing. The week between Iowa and New Hampshire may be the final week of the Trump campaign, because if he goes 0-2, he will not be the nominee. It's never happened before in the GOP, although the sheer size of the field this year makes breaking this precedent possible. Trump may very well win New Hampshire, with then South Carolina and the Southern primary on March 1 will provide significant clarity. New Hampshire may be Trump's last stand. We do not know how he will handle the pressure.

I believe Trump has a 10 percent chance to be the nominee as the race currently stands. Cruz and Rubio are well-positioned, and Christie has a real chance to steal New Hampshire. The winner-take-all states that vote starting March 15 will decide the nomination. Trump has had a stellar second half of 2015, but the first two months of 2016 may be a different story entirely.

This piece has been corrected to note that only New Hampshire independents can vote in either party's primary; registered party members can only vote in their respective party primaries.

Mackowiak is syndicated columnist; an Austin, Texas-based Republican consultant; and former Capitol Hill and George W. Bush administration aide.