Here’s the thing. Trump had to know his best shot at winning the nomination was winning Iowa and then running the table and he didn’t do the investments necessary to turn out low propensity voters. 5,000 voters made the difference. That’s a small Trump crowd in much of the country. Who knows what difference a few more offices around the state, a few dozen more staff, some more TV ads could have made. He was cheap and he probably knows it.
Now, it gets to be a messy 3 person race. Rubio will quickly consolidate the establishment lane. Cruz will get the hard right evangelical lane, and Trump the populist lane.
Trump skipping the debate created a vacuum that allowed Rubio to shine. It was a gamble but would it have been any better if Trump showed up? I doubt it. Maybe it would have been worse. The debate would have been an ambush with video montages, muslim trump haters asking questions, etc. Any of his interactions with Megyn Kelly would have been psychoanalyzed for sexism by the media. Any statement made out into a gaffe. It could have created a whole weekend of drama before the Iowa caucus. Instead Cruz got hammered. But it did create a vacuum for Rubio that wouldn’t otherwise have been there.
Skipping the debate could end up being the trigger that gives us Rubio as our nominee. Funny how life works out.