On this day in 1971 South Dakota Sen. George McGovern announces his presidential campaign. Now for today's top stories:

"S.C. Primary May Yield GOP Front-Runner, Answers" (David Jackson, USA Today) Or it just as easily could not, one guesses. Even though every GOP nominee in recent history has won South Carolina, the game is different today. One thing is clear, however: Whatever happens tomorrow will change what we think we know about this race.

"Romney Leaves South Carolina to Focus on Nevada Caucus" (Adam Nagourney and Michael Luo, New York Times) Just days after winning Michigan, Romney has pulled out of South Carolina, all but yielding it to John McCain or Mike Huckabee (or someone else). Nevada isn't as important, but it does have more delegates, which, down the road, could prove the most important thing.

"Poll: Nevada Going to Clinton, Romney" (Molly Ball, Las Vegas Review-Journal) A new Nevada poll has Hillary Clinton up 9 points over Barack Obama. Mason-Dixon, which conducted the poll, found that Hillary is winning women over 50 and the Hispanic vote.

"Judge allows special caucuses at 9 Vegas casinos" (Johanna Neuman, Los Angeles Times) An important ruling from a Nevada judge allows casino workers the chance to caucus in their workplaces. Since the Culinary Workers Union, which represents casino workers, has endorsed Obama, the ruling is seen as a significant victory.

"Romney Gets Testy Over Issue of Lobbyists in His Campaign" (Michael Levenson, Boston Globe) Actually, it was AP reporter Glen Johnson who got testy, while Romney stayed remarkably cool and even invited the reporter to discuss the matter further with him later. We'll be watching to see if reporter Johnson brings the same level of skepticism to other candidates he covers.

"Southern Blacks Are Split on Clinton vs. Obama" (Shaila Dewan, New York Times) Black voters are expected to constitute between 20 and 50 percent of the vote in South Carolina (whose Democratic primary is on Jan. 26) and in the four southern states with primaries on Feb. 5. Although popular opinion is sliding toward Obama, black leaders are torn between him and Hillary.

"Huckabee Says Let SC Decide on Flag" (Libby Quaid, Associated Press) To a cheering crowd, Mike Huckabee stepped right into the Confederate flag issue, which always seems to come around near primary time, with a joke: "In fact, if somebody came to Arkansas and told us what to do with our flag, we'd tell 'em what to do with the pole, that's what we'd do."

"Thompson Hopes S.C. Revives His Campaign" (Dan Balz and Perry Bacon Jr., Washington Post) Last-stand time for Fred Thompson? That's how it's being played in the media, although Fred insists that even a loss here, which is likely, won't end his run. Who knows, but with the race the ways it's been going recently, it's unwise to count out anyone at this point.

"Labor Makes Big Comeback in '08 Races" (Brody Mullins, Wall Street Journal) Despite declining membership, Big Labor has regained its position as "the single-strongest force in elections," according to reporter Mullins. Where Labor is excelling is in the ground game, getting the voters out, which, combined with deep pockets, makes for a powerful force.

"Limbaugh's Praise for Romney's Run Heard Loud and Clear" (Michael Levenson, Boston Globe) How might Rush Limbaugh's praising of Romney, and bashing of Huckabee and McCain, affect voters' opinions?

Get these and today's other stories at RCP's Politics and Election page.