South Carolina primary: What to watch as the votes come in

Republican presidential candidates, former Pennsylvania Sen. Rick Santorum, former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich, Rep. Ron Paul, R-Texas, during the Republican presidential candidate debate at the North Charleston Coliseum in Charleston, S.C., Jan. 19, 2012.
AP Photo/David Goldman
GOP presidential debate in South Carolina
Republican presidential candidates, Rick Santorum, Mitt Romney, Newt Gingrich, and Ron Paul, during the Republican presidential candidate debate at the North Charleston Coliseum in Charleston, S.C., Jan. 19, 2012.
AP Photo/David Goldman

Since the 1980's the South Carolina Primary has sought to be the first voice of southern Republicans - even scheduling itself on Saturdays to help do that - and has always played a crucial role in GOP nomination contests. With the pre-election polls now tightened between Mitt Romney and Newt Gingrich, it could be pivotal again. Here are some things to watch as the votes start rolling in.

The voters:

This primary contest boasts has a number of important groups to watch and they include:

Tea Party voters: So far in this primary season, Tea Party backers have given enough of their support to Romney to keep him in the top tier; in fact in New Hampshire he got very strong backing from them. But South Carolina has been a hotbed of Tea Party activism in the last couple of years - will they go for Romney the same way? In pre-election polls, Tea Party backers in South Carolina tilted toward Gingrich over Romney. They could be decisive Saturday.

Republicans: It might sound odd to write that, but the point is that the party's base - people who consider themselves partisans - is likely to play a much bigger role in South Carolina than it did ten days ago in New Hampshire. Although anyone can vote in the South Carolina primary (and there is no formal party registration), self-described independents usually don't choose to participate at the same rate that independents do in New Hampshire. Only one in five voters in 2008's primary were independents - whereas in New Hampshire ten days ago, almost half the electorate was. In short, the winner Saturday will likely need to win the base.

Evangelical voters and social conservatives: After spending and debt issues dominated the last cycle, there has been a lot of talk now centering on values issues, too. Rick Santorum is vying for the votes of social conservatives and they could be crucial to his fortunes as they were in Iowa. In 2008, half the South Carolina electorate were evangelicals.

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The regions:

We've seen different voting patterns by region in South Carolina, so watching where the votes are coming from is critical.

The coastal regions of the state, from Hilton Head and up to Charlston, backed John McCain in '08, and this could be territory - with its retirees, higher-income voters, veterans, and part of an area that has been fast-growing - that Romney may need to win now. McCain doubled up on Huckabee here, giving him the edge statewide.

Keep an eye on the Piedmont region, a vote-rich, deeply conservative northwest corner of the state. The counties surrounding Greenville and Spartanburg typically account for about 3 in 10 votes statewide, but in a high-turnout GOP primary, could turn out in force and can cast four in ten of the ballots. To win in South Carolina you have to at least do well here. Huckabee beat McCain by 6 points in this region. Meanwhile, as he was running fourth in the primary, Romney in 2008 had one of his relatively best showings in Greenville. This may be where Gingrich and Santorum will want to make inroads. (But whether or not they split any anti-Romney vote, or one of them gets the lion's share of it, could determine the outcome, too.)

To show where the vote comes from, this map illustrates the counties by the size of their voting population, not their geographical size. You see the population centers along the coast, up around Greenville and Spartanburg, and the smaller rural counties around the outskirts of Columbia.

Rural counties are important too, in the aggregate. In 2008, they were not friendly to Romney; his relatively worst performances were in the counties ringing Greenville, the rural counties along the North Carolina border, and the rural counties between Columbia and Myrtle Beach.

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    Anthony Salvanto is CBS News elections director