Rick Santorum's double victory in the South definitely left many in the Congress and in political circles in Washington, D.C. surprised, with many wondering just how far Santorum can push Mitt Romney in this GOP nomination race.

"It was invisible," Sen. Thad Cochran (R-MS) said of Santorum's late primary surge in Mississippi.

"I was surprised," Cochran told me as he waited for the subway to take him to his office on the Senate side of Capitol Hill.

Instead of babbling on endlessly about what happened, I want to put up two graphics of the states and let you hash out the reasons why Santorum won, why Gingrich finished second and why Romney was third.

First, let's start with Alabama:

And now a look at Mississippi - note how Santorum swept every county in the far north of of both states along the border with Tennessee: