Just a week ago, Mitt Romney was up double digits and was on course to cruising to his third win in three contests.

Tonight, however, it was Newt Gingrich who won big. And, Romney is now only one for three.

What happened?

Three big things:

1)      Romney's taxes:  Or actually, the fact that he hasn't released them - yet. Romney has spent more time defending his personal wealth than just about anything else. And, he hasn't done a particularly good job defending it either.

2)      Debates: Gingrich dominated, while Romney stumbled. Gingrich did a masterful job of training his fire on the mainstream media - a surefire way to excite the base.

3)      Rick Santorum: He was supposed to compete with Gingrich for that conservative vote. But, in the end Gingrich won almost 50 percent of those voters who described themselves as conservative, while Santorum took just 20 percent. Without Santorum splitting up the anti-Romney vote, Gingrich had a clear path to the win.