Nate Silver notes via Twitter that his compilation of past primary polls shows that pollster error in Alabama and Mississippi "has been about 50% higher than in other states." Also, as blogger Harry Enten points out, three of the final four polls on the Alabama Republican primary in 2008 showed Sen. John McCain (R-Ariz.) leading former Arkansas Gov. Mike Huckabee -- two polls showed McCain leading by fairly wide margins. Yet Huckabee defeated McCain, 41 to 37 percent.

Given the close and inconsistent findings of the final polls in Alabama and Mississippi and the poor track record of past horserace polling there, the potential for a Tuesday night surprise is significant.

Despite the close numbers, Philip Klein doubts Romney will be able to pull off wins in either Mississippi or Alabama: