Gingrich isn’t on the ballot in the Missouri “beauty contest” primary, and Paul trails badly. Missouri is pretty much a one-on-one match between Romney and Santorum. A Santorum victory would slow Romney’s momentum—and would certainly give Santorum a boost—going forward.

In Minnesota and Colorado, the caucus system will result in a proportional allocation of delegates among the various candidates. But with polling showing Santorum even with Romney in Minnesota and second to Romney in Colorado, a strong showing for Santorum would do the most to slow the Romney juggernaut. It would also of course help Santorum’s chances to replace Gingrich down the road as the alternative to Romney—an outcome that, I suspect, might well result in a better race for the nomination and a healthier situation for the ultimate Republican nominee.