Given the stakes at play, here's what to look for as the results come in Tuesday. Does Mitt Romney finally win a Southern state or two? — It's hard to think of a Northern Republican since, say, the first Union generals of the Civil War, who has had as little success in the South as Romney. OK, that's an exaggeration but it makes the point. He failed to win the first Southern state to vote in the primaries — South Carolina in January — and the three that followed. (OK, so we're not counting Florida as a real Southern state.)

Ron Paul of Texas — the 26 at-large delegates, for instance, will be awarded proportionally based on the percentage of the statewide vote each candidate receives, so long as he gets at least 20 percent of the vote. Similarly, if a candidate is able to garner more than half the votes in any of Alabama's seven congressional districts, he will get all three of that district's assigned delegates. And if no one gets a majority, the candidate with the most votes gets two district delegates while the runner-up gets one. Confused yet? Does Newt Gingrich extend his victories in the South? — Gingrich has said he must win in Alabama and Mississippi to remain viable. He eschewed campaigning in Kansas where caucuses were held over the weekend to spend his time instead in the two Deep South states with Tuesday primaries. If he wins one state outright and does well in the second, that would give him a hot rolled steel coil argument for continuing.

So it will be important to watch exit polls to see how much they split that vote. That could help Romney. How big a factor was rising gas prices to voters? — Gingrich has recently made his stand in Dixie by vowing to get gas prices down to $2.50 a gallon amid rising prices at the pump that have hurt President Obama's approval ratings. Gingrich has saturated the airwaves in Alabama and Mississippi with his gas-price message. Exit polls will likely ask voters about their concerns about the economy and gas prices, and their answers may provide clues about the effectiveness (or not) of Gingrich's strategy.

But Romney is showing surprising, last-minute strength in Alabama and Mississippi, thanks to his organization and money. A win Tuesday in either of those states would end that string and allow Romney to boast that he can, indeed, win in the region that for more than a generation has been the Republican Party's crucial bastion.

What percentages do the candidates win? — Because the race for the Republican presidential nomination now boils down to a complicated delegate chase, it will be important to look at the percentages of the vote each candidate wins in each state and the congressional districts within the states. In Alabama, there are 50 total delegates at play — 26 at-large delegates, 21 congressional district delegates and three so-called automatic delegates. If no candidate wins a majority of the statewide vote — which is likely, given it's a four-way race that also includes Rep.

Short of that, it will look like the end of the road for his campaign. How much do Santorum and Gingrich split the support of evangelicals and very conservative Deep South voters? — Both Santorum and Gingrich have been appealing to the same very conservative voters and religious voters