I’ll have more to say about all this in my column tomorrow. But this is the night Santorum needed. First, the pressure on Gingrich to bow out will grow substantially — and even if Gingrich doesn’t actually quit, it has become clear that Santorum is the one plausible conservative challenger to Mitt Romney. Second, after spending heavily, Romney ran third in both states. This guarantees more stories and endless commentary on the weakness of the front-runner. It will require Romney to keep veering to the right, which can’t be helpful to him in the fall if he eventually does prevail to win the nomination.

For those who like to watch election nights, the Alabama and Mississippi results are a tonic. They’ll keep things going in the Republican race for some time.

Earlier: The Dixie primaries and the 2 percent solution