Only a week ago, it looked like Mitt Romney might make history by winning Iowa, New Hampshire, and South Carolina, which no candidate had ever done before. But now it looks like a different candidate will win each of the first three nomination contests, which has never happened before, either. Worse for Romney, his poll numbers are falling not just in South Carolina, but nationally, too. Here's our guide to today's polls and why they matter.

Findings: Gingrich is beating Romney in South Carolina 32 percent to 26 percent.
Pollster: Clemson University
Methodology: Phone survey of 429 likely voters that began January 13 but was "recalibrated… to measure changing dynamics" January 18 and January 19.
Why it matters: This poll confirms the findings of three robo-polls released Thursday. Romney seems to believe it, too, because he's trying to lower expectations, The Hill's Christian Heinze writes. Romney said it was "exciting" to be in a close race, and noted Gingrich was from a neighboring state. A Public Policy Polling survey released late Thursday night said Gingrich was enjoying higher favorability ratings than Romney for the first time in this election.
Caveat: The poll finds 20 percent of voters are still undecided, with polls opening in less than 24 hours. 

Findings: Romney's support nationally has been cut by more than half in less than a week, from 23 percentage points to 10 percentage points. Romney is still ahead, 30 percent to 20 percent.
Pollster: Gallup
Methodology: Phone interviews with 1,235 Republican and Republican-Leaning voters from January 15 to January 19.
Why it matters: This poll captures some of the effects this week's surprising events have had on voters, including Jon Huntsman and Rick Perry quitting, Marianne Gingrich giving her first TV interview, Rick Santorum retroactively being declared the winner in the Iowa caucuses, and Romney struggling to answer why he won't release his taxes. "Polls in South Carolina suggest that Gingrich has a good chance of winning that state, and if so, the race could tighten further in the coming days," Gallup's Frank Newport writes.
Caveat: It's possible more discussion of Gingrich's past marriages will hurt him, especially with women voters. In a general election between Gingrich and Obama, Gingrich loses women by 18 points, according to a recent poll, the Washington Post's Felicia Sonmez reports. And Romney's appeal to women helped him crush his competitors in New Hampshire. On the other hand, the Republican electorate is disproportionately male. 

Findings: Rick Perry returns home to Texas with an approval rating of 42 percent—two points lower than President Obama's in the state. In a hypothetical election against Obama, the governor is ahead by a single point in his deep-red home state.
Pollster: Public Policy Polling
Methodology: Robo-calls to 700 Texas voters January 12 to January 15.
Why it matters: Running for president looks like so much fun that some guys do it just to sell books. But it can come at a cost. Perry has fallen shockingly far in less than six months. He was beating Obama by 7 points in September, the pollster found.
Caveat: PPP leans left.