LIVE VIDEO: Watch the Super Tuesday Showdown
We're live-blogging results from Super Tuesday, where voters in 10 states are casting ballots in the GOP presidential race.
Scroll down for highlights.
11:05 p.m. ET
Romney and Santorum are trading leads in Ohio, in what for some political junkies is a reminder of the count in Iowa. A couple thousand votes separate them.
11:02 p.m. ET
Fox News is projecting Romney wins the Idaho caucuses.
10:47 p.m. ET
Santorum has sent out a fundraising pitch headlined: "We Won!"
"We are just starting this fight," the former Pennsylvania senator says.
10:27 p.m. ET
AP says Santorum wins North Dakota.
10:26 p.m. ET
Some interesting tidbits from the states: In Virginia, where only Romney and Paul were on the ballot, Romney won 10 of the state's 11 congressional districts. Paul did best in the 3rd District, which includes Portsmouth.
10:23 p.m. ET
What concerns Ohio voters? Check out our graphic of the exit polls in the Buckeye State.
10:07 p.m. ET
CNN is projecting that Santorum will win the caucuses in North Dakota. That would make three states for him and three for Romney.
9:59 p.m. ET
Romney notes he has cut taxes 19 times in Massachusetts. "I stand ready to lead our party and I stand ready to lead our nation to prosperity," he says. The crowd is chanting: "All the way!"
David Jackson will have more on Romney's remarks in On Politics.
9:52 p.m. ET
"You have a president that's failed you," he says to people who are looking for a job. "And that's going to change."
The crowd is chanting "USA! USA!"
9:48 p.m. ET
He congratulates Gingrich and Santorum on their victories, and gives a nod to Paul and his enthusiastic supporters.
"I"m not going to let you down. I'm going to get this nomination," Romney says, vowing to go all the way to the White House.
9:20 p.m. ET
"This campaign is about the towns that got left behind and the families that made those towns the greatest in this country," Santorum says. "This was a big night tonight. We're going to win a few and lose a few. We're going to get at least a couple of gold medals and a whole passel of silver medals."
9:17 p.m. ET
Santorum is speaking from a high school, where the gymnasium's weight room doubled as his war room.
"This is where we're from," he says about the Ohio-West Virginia region. He introduces his mom, Kay, who is 93 years old, and his in-laws, the parents of his wife, Karen.
9:16 p.m. ET
Rick Santorum and his family are making their way onstage in Steubenville, Ohio. The race there is too close too call.
9:11 p.m. ET
AP says Santorum wins Oklahoma.
9:01 p.m. ET
CNN says Santorum wins Oklahoma. Ohio, one of the big states to watch tonight, is still too close to call.
8:52 p.m. ET
Gingrich says tomorrow is a "new chapter and fight for the soul of the Republican Party. It's a chapter and fight for who we are as Americans."
And he says: "I am the one candidate who has the ability to debate Barack Obama."
David Jackson has full coverage of Gingrich's remarks in the On Politics blog.
8:48 p.m. ET
"There are lots of bunny rabbits that run through. I am the tortoise," Gingrich says about his standing in the GOP race.
He said if he couldn't carry his home state he would have "no credibility" as a candidate.
8:43 p.m. ET
Gingrich starts by chastising those in the media who counted him out of the GOP race. "We survived the national elite's efforts to kill us in the summer because of you," he says to his supporters. "We survived the two most difficult months of a career."
Gingrich said the "elites ... thought a Gingrich presidency was so frightening that they had to kill it. But you wouldn't let them do it."
8:41 p.m. ET
AP says Santorum has won Tennessee.
8:39 p.m. ET
Gingrich is about to speak to his supporters gathered in Atlanta.His wife, Callista, is thanking the crowd and introducing the former House speaker.
"Our only opponent is Barack Obama," she says.
8:37 p.m. ET
CNN is reporting that Gingrich will receive Secret Service protection starting tomorrow. Santorum and Romney already have such protection.
CNN also says Santorum will win Tennessee.
8:24 p.m. - 8:30 p.m. ET
CNN's Wolf Blitzer is asking Palin if she wants to weigh in on the Rush Limbaugh controversy.
Palin says it is the "definition of hypocrisy" that Limbaugh was "called out and forced to apologize" for calling Georgetown University student Sandra Fluke a "prostitute" and "slut." She said the same standard is "never applied" to "leftist radicals."
Asked if she would run for president if the GOP campaign comes down to a brokered convention, the 2008 GOP vice presidential nominee said she wouldn't close the door to the idea.
8:23 p.m. ET
CNN is talking to former Alaska governor Sarah Palin, who just cast a ballot in her home state but won't say which Republican got her vote.
"I want to see the process continue," she says, adding that she wants to see which candidate can bust through Obama's "Orwellian rhetoric" and who has the best ideas for the economy.
"Competition makes all of our candidates better," Palin says. "Obama is the worst choice."
8:11 p.m. ET
Romney will also make note of the long campaign ahead of him, according to excerpts of his remarks released by his campaign.
"Tonight we've taken one more step toward restoring the promise of America. Tomorrow we wake up and we start again. And the next day we do the same. And so it will go, day by day, step by step, door to door, heart to heart," he will say.
8:08 p.m. ET
The Romney campaign is sharing excerpts of the remarks he'll make tonight, and it looks like the GOP candidate will spend a good bit of time criticizing President Obama.
"This President is out of ideas. He's running out of excuses. And, in 2012, he'll be out of office," Romney will say.
David Jackson will have more later here in On Politics.
8:04 p.m. ET
Fox News is projecting Santorum will win Oklahoma. Seven states have now closed their polls. Alaska, Idaho and North Dakota are holding caucuses that will run late.
8:01 p.m. ET
AP has called Romney the winner in Massachusetts. He was governor in the Bay State from 2003 to 2007. The fall campaign will feature a key Senate race between Republican Scott Brown and his likely Democratic challenger, Elizabeth Warren.
8 p.m. ET
CNN projects Romney, a former Massachusetts governor, will win his home state.
7:56 p.m. ET
Polls will close shortly in Oklahoma, Massachusetts and Tennessee.
7:43 p.m. ET
AP says Romney has won Vermont.
7:40 p.m. ET
Ron Paul is speaking to his supporters in North Dakota, which is holding caucuses. The polls there close at 10 p.m. ET.
CNN is covering the speech live. Paul gets huge cheers with his call for getting rid of the Federal Reserve, one of his big causes. "A better deal can be found in less government and only sending people to Washington who read the Constitution," the Texas congressman says.
7:37 p.m. ET
NBC and CNN are projecting Romney will win Vermont. That would be two states for Romney and Georgia goes with Gingrich.
7:30 p.m. ET
The polls are now closed in Ohio and we can start to report on exit polls. More than 30% of the voters in early exit polls said they were "very conservative," and Rick Santorum was leading among those voters.
Among the voters who said defeating Obama was a key reason for their vote, a majority of those voters were behind Romney.
7:24 p.m. ET
AP says it's a win for Romney in Virginia, a key battleground for the fall. In 2008, President Obama became the first Democrat to win the Old Dominion since Lyndon Johnson did it in 1964. The state will also be one to watch in the fall because of its Senate race, which will likely feature two former governors: Republican George Allen and Democrat Tim Kaine.
7:21 p.m. ET
CNN is also calling Virginia for Romney.
7:18 p.m. ET
NBC is projecting Romney will win Virginia. The interesting thing to watch will be his share of the popular vote. If he tops 50%, he'll win all of the at-large delegates. The rest are allocated by the winner of congressional districts.
7:13 p.m. ET
Gingrich just tweeted that it "is gratifying to win my home state so decisively to launch our March Momentum." He's also hoping to do well next week when the GOP race moves to Alabama and Mississippi.
7:11 p.m. ET
The Associated Press reports that Gingrich will pick up at least 23 of Georgia's delegates, which are awarded by proportion of the statewide vote.
The polls are closed in Vermont and Virginia, and Romney is leading in both of the states based on exit polls of the TV networks.
7:03 p.m. ET
Gingrich, who represented a Georgia district in Congress from 1979-1999, had said he needed to win his former home state to stay "credible" in the race. He did not vote today in Virginia, where he now lives, because he did not qualify for the ballot.
7:01 p.m. ET
And it's official: The Associated Press calls Gingrich the winner in Georgia, his former home state.
7 p.m. ET
CNN is projecting Newt Gingrich will win Georgia and its 76 delegates.
6:40 p.m. ET
USA TODAY's Jackie Kucinich is on the ground in Ohio, one of tonight's big battlegrounds.
She reports that Mitt Romney's campaign launched an automated robo-call encouraging voters to go back and vote in Franklin County, Ohio after there were press reports that a "small number" of voters had left polling places without casting a ballot due to confusion among poll workers.
Romney spokesman Ryan Williams confirmed the calls went out and said they learned of the problems at polling places from news reports.
Ben Piscitelli, spokesman for the Franklin County Board of Elections, told the Columbus Dispatch the confusion stemmed from ballots used by multiple precincts.
In places where all of the precincts had the same candidates and issues on their ballot, Piscitelli said, ballots were issued for one precinct and were expected to be used for all of them.
For example, the polling place for precinct A, B and C would have only ballots for precinct A because all three are the same. But poll workers looking for the B and C ballots could not find them, and didn't know they were supposed to use the A ballot for all voters.
There are 110 polling places that have multiple precincts with identical ballots, Piscitelli said.
"We ended up calling all of them and explaining it to them," he said. "But we know some people left without voting."
Updated 6:35 p.m. ET
Polls will close first in Vermont, Georgia and Virginia.
Our original post begins here:
Mitt Romney and Rick Santorum were neck and neck in polls in all-important Ohio, a key battleground for both political parties in the fall. Newt Gingrich is poised to take his former home state of Georgia, the night's biggest delegate prize. And Ron Paul campaigned hard in states holding caucuses such as Idaho and Alaska.
The 10 states have a total of 437 delegates, including the so-called "super delegates" who are guaranteed slots at the GOP convention in Tampa.
Our colleague David Jackson will also be blogging highlights in the On Politics blog, and our political team will have full coverage in Wednesday's editions.