If Cruz pulls out a surprise and wins the caucuses in the face of an all-out push against him by the GOP establishment, it would give the campaign strong momentum going into New Hampshire and then the Southern primaries, where he is perhaps better positioned than any other candidate to do well. A follow-on runner-up showing in New Hampshire, would put all of the other non-Trump candidates on the ropes and would leave the GOP establishment looking at a fairly clear (if unpleasant, to them) choice between Cruz and Trump as the nominee. If Cruz places a solid second, in Iowa, as expected, he will still go into New Hampshire as the leading Trump alternative, though the stakes will be higher in New Hampshire. While the GOP establishment will do their best to downplay Cruz’s showing regardless of the result, Only if Cruz finishes an unexpectedly distant third in Iowa would his prospects be substantially dimmed.
As for Rubio, the calculus is a bit trickier. If he pulls of an unexpected win, he would carry strong momentum in New Hampshire and would expect to see a surge of establishment endorsements and money line up behind him. A win or strong second there would leave him in a very strong position to be an alternative to Trump. If Rubio places second in Iowa, he would also be in a good position to carry momentum into New Hampshire, and a 2nd place showing there would put him in a good position going into SC and Nevada, though he is not as well positioned as Trump or Cruz for the “SEC Primary.” Rubio’s team has done a nice job tamping down Iowa expectations, but if, after hopes have recently risen, he scores only in the low to mid teens, or worse, somehow gets caught by Carson, his star may be eclipsed.
But in any of these scenarios, it seems that Trump, Cruz and, (most likely) Rubio aren’t going away anytime soon, nor will Trump, with his sky-high negatives, simply be able to shock-and-awe his way to a GOP primary victory. Barring something very unexpected in tonight’s Iowa results, those fundamentals aren’t going to change.