Voters in Alabama and Mississippi head to the polls on Tuesday in a pair of primaries that could reshape the Republican race, as well as caucuses in Hawaii and American Somoa. Here’s are five key questions in the GOP nomination process to think about before Tuesday’s votes come in.

1. Why is the GOP primary still going on?

Former Massachusetts Gov. Mitt Romney’s campaign is accurately arguing that, because of his lead, and the rules of the GOP primary (he keeps collecting delegates even in states he loses because they are rewarded on a proportional basis), Romney is almost certain to emerge ahead of his rivals after all the primaries are completed in June.

But ex-Pennsylvania senator Rick Santorum, in particular, has an obvious reason to stay in the race; he has drubbed Romney in some key states, such as his 30-point win on Saturday in Kansas. Romney is struggling to defeat Santorum in the Midwest, the South, and among Tea Party and evangelical voters, who are a huge part of the GOP base.

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2. Can Romney get a win in the Deep South?

Romney won the primaries in Florida and Virginia, but lost to his rivals in Georgia, South Carolina and Tennessee. Some polls in Alabama and Mississippi have shown Romney effectively tied with former House Speaker Newt Gingrich and ex-Pennsylvania senator Rick Santorum.

Gingrich and Santorum are fighting for the same Tea Party, evangelical voters. And if Gingrich is as strong as the early polls have shown him to be in these two states, he could pull away votes that might otherwise go to Santorum, allowing Romney to win by dominating the vote among more moderate Republicans, who are focused on electability.

A Romney win in either state would quiet some of the criticism that he is unable to connect with the base of the GOP.

3. Is Gingrich done if he doesn’t win either state?

The candidate and his team have not said exactly what Gingrich will do if he can’t win Alabama or Mississippi, but two defeats, in the area of the country he has cast as his strongest, would likely depress support for his candidacy. Key conservative outlets, such as FOX, would be less likely to treat Gingrich as a serious contender if he can’t win in either state.

4. Are Gingrich and Santorum blocking one another from defeating Romney?

Yes and no. If either candidate could collect most of the Tea Party, very conservative and evangelical votes, it would certainly help them accumulate delegates and narrow the margin against Romney. In many of the primaries, including Alabama and Mississippi, a candidate getting a majority of the statewide vote would collect a huge haul of delegates.

But it will be hard for Gingrich, Santorum or even Romney to win 50 percent with three candidates splitting the vote, particularly if a race is close.

At the same time, to truly catch up, Santorum or Gingrich must start winning big states with lots of delegates, such as Florida, Michigan and Ohio, all of which Romney carried. And one of them must start winning over Romney with large margins, as Santorum did in Kansas but has not done in most other states.

In that sense, the more important primary this month may be on March 20 in Illinois, particularly if Gingrich is out of the race and Santorum can try to get a majority of the vote there.

(One important caveat is that the dynamics of the race will change if Romney and Santorum are effectively one-on-one; i.e. Romney could start using his advantage in campaign money to truly pummel Santorum if a primary gets too close)

5. What does all of this mean for President Obama?

Very little. Some Republicans are wary of a longer primary, but it’s not clear that’s a big danger: Obama easily won the 2008 general election after an extra-long primary contest against Hillary Clinton.

Job growth, the unemployment rate, and other factors will likely shape the president’s reelection chances much more than the GOP primary process.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr