Saturday’s Republican primary in South Carolina could be the last chance for Newt Gingrich, Rick Santorum and Texas Rep. Ron Paul to mount a serious challenge to front runner Mitt Romney. The Post polling team will be crunching exit poll data throughout the night, but here are five factors that seem key going into primary day.

1. Battle of the sexes

Men have driven Gingrich’s late surge in pre-election polls, but his numbers haven’t improved much among women. Gingrich won 28 percent support among men in a CNN/Time/ORC poll released Wednesday, compared with 16 percent among women.

It’s not clear how much impact, if any, the latest brouhaha over Gingrich’s problems with his ex-wife will have on voters Saturday, or which candidate stands to benefit. Regardless, South Carolina may mark the first contest with a significant – and potentially decisive – gender divide.

2. Religious divide

Self-identified born-again Christians propelled Rick Santorum in Iowa and he looks to outperform among this group in the Palmetto State as well. Still, polls show him battling Paul for third and far behind Romney and Gingrich.

The critical question is whether Romney can limit his losses among evangelicals and maximize his margins among those who don’t identify as born-again Christians. In the 2008 South Carolina primary, Romney did nearly twice as well among non-evangelical voters as he did among evangelicals (20 vs. 11 percent). This year in Iowa, he performed 24 points worse among born-again Christians than among other voters (38 vs. 14 percent).

3. South Carolina’s tea party like Iowa’s or N.H.?

Romney fared quite poorly among the strongest tea party supporters in the Iowa caucuses, but carried this group by double digits in the New Hampshire primary. Pre-election polls this week show Gingrich consolidating support among this group, but it remains to be seen how many will turn out and whether Romney can hold his ground.

4. Older voters

Romney’s support peaked among older voters in Iowa and New Hampshire, and the latest Washington Post-ABC News national poll found Romney winning 49 percent of Republicans and GOP-leaning independents ages 65 and older. But pre-election polls show his lead among older voters shrinking in the past week. Saturday’s exit polls will reveal if this Romney calling card has run out of minutes.

5. Romney’s Bain

Romney faced an onslaught of attacks in South Carolina for his work buying and restructuring companies while working at Bain Capital. The state has a 9.9 percent unemployment rate and fully 50 percent of 2008 primary voters lacked a college degree; a key target of ads highlighting Romney as a man who endangered jobs of ordinary people.

.Still, there’s little evidence that such attacks have taken root. More than twice as many likely voters said the attacks were unfair than fair to Romney in an NBC News/Marist poll released this week. And more than six in 10 in the poll said investment firms like Bain help the U.S. economy; about a quarter say they hurt it. Nationally, Republicans have soured somewhat on Romney’s work restructuring companies, but it remains a net positive in the latest Post-ABC poll

Catch the latest coverage on the South Carolina primary on the Post’s Election 2012 blog.

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