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While Iowa caucusgoers are kicking off the official 2012 Republican presidential nominating contest, in the social media realm among users nationwide, Texas Rep. Ron Paul already is in the lead, according to a data analysis of Facebook use by Socialbakers, which collects social media statistics.

Former Massachusetts Gov. Mitt Romney eked out an eight-vote win after he and former Pennsylvania Sen. Rick Santorum swapped the slimmest of leads back and forth in Tuesday's caucuses. With returns complete, each had won the support of roughly 25 percent of caucusgoers.

In 2008, young voters turned out in droves to elect Barack Obama, but now seem less likely to support his re-election campaign. Some young liberals have even thrown their support behind Republican Ron Paul.

In a last-minute pitch he hoped would make inroads with voters concerned about electability, Gingrich waxed nostalgic about Ronald Reagan and derided Washington as "cloud cuckoo land."

NPR's Don Gonyea and Ari Shapiro have been traveling through Iowa these last few days and weeks. They join Robert Siegel to talk about Tuesday's caucus vote.

Iowans gather Tuesday evening for the state's precinct caucuses. A group of caucus-goers talks about who they plan to vote for and how they made up their minds.

Republican presidential hopefuls were bearing down and trying to sway voters hours ahead of the first major test of the primary season. But more than a third of those participating in the state's caucuses say they still haven't made up their minds.

After months of campaigning, it's finally caucus day in Iowa. Polls still show a fluid race, with former Massachusetts Gov. Mitt Romney, Texas Rep. Ron Paul and former Pennsylvania Sen. Rick Santorum heading the pack.

And the race could go any which way, because 41 percent of Iowa caucus goers remain undecided. The caucuses start at 8 p.m. ET.

As Iowa Republicans head to the caucuses to have their say, we look at how the candidates stack up on the eve of the vote — and how previous winners (and losers) eventually fared.