Would Obama make the South competitive?

Mississippi voters head to the polls today, their 40 delegates -- 33 unpledged, seven supers -- suddenly important thanks to the tight Democratic race.

In a state where 55% of the Democratic primary electorate is African-American, Obama is heavily favored. If he wins, it will be Obama's fifth Deep South victory (he's taken Alabama, Georgia, Louisiana and South Carolina; Clinton succeeded in the periphery states of Arkansas, Tennessee and Texas).

Obama's ability to run up huge primary victories in the Deep South leads to a bigger question: could he make the South competitive for the Democrats?

A recent Wall Street Journal piece pointed out that even if Democratic prospects for winning Deep South states was low -- "White voters in Mississippi don't vote Democratic. They just don't," the oft-quoted Charlie Cook said -- Obama could still change the 2008 election dynamic.

Obama's high African-American voter turnout and cross-over appeal to independents -- combined with John McCain's questionable relationship with Southern evangelicals -- would at the very least force Republicans to invest precious resources in states that haven't been on their radar for years:

If Mr. Obama wins the nomination, it is far from certain that he could claim even a single Southern state. But even making the race there competitive would be a victory of sorts by forcing Mr. McCain to spend time and money defending states that other Republicans, including President Bush, were able to take for granted.

UPDATE: MSNBC's First Read adds this:

In fact, Mississippi is one of those rare Southern states that might be in play in the general election if Obama becomes the nominee. One Dem statistician tells First Read that there are three red states that could swing if African-American turnout was ever maximized (both in registration and in actual turnout): Georgia, Louisiana and, yes, Mississippi.