Updated: 1:19 a.m. ET
(CBS News) As votes rolled in across America on Super Tuesday, Mitt Romney, Rick Santorum and Newt Gingrich split Republican support between themselves, with Romney and Santorum poised to win several contests each and Gingrich set to win in his home state in Georgia.
CBS News projects Mitt Romney will win Republican presidential nominating contests in Ohio, Virginia, Idaho, Massachusetts and Vermont. CBS News projects Rick Santorum will win primaries in Tennessee and Oklahoma, as well as the North Dakota caucuses. In Georgia, CBS News projects Newt Gingrich will clinch his first primary victory since South Carolina's January 21 primary contest.
In the battleground state of Ohio, where polls closed at 7:30 p.m. ET, the race was neck and neck, with CBS News projecting a slim victory for Romney.
There are also caucuses in Alaska. Results are expected later this evening.
With voters in ten states selecting their choice to be the Republican presidential nominee and 419 delegates up for grabs, Super Tuesday could be a make-or-break night for the remaining Republican presidential candidates.
Romney stayed positive in remarks to supporters Tuesday night, saying the campaign was "going to get more" wins under its belt by the end of the night, and that by his count, the delegate situation "looks good."
"Tonight, we're -- we're doing some counting. We're counting up the delegates for the convention, and it looks good. And we're counting down the days until November, and that looks even better," Romney said.
The candidate went on to accuse President Obama of being "unresponsive" to the wishes of the American people, and blasted him for allegedly operating "by command instead of by consensus."
"President Obama seems to believe he's unchecked by the Constitution," Romney told an enthusiastic crowd in Massachusetts. "He's unresponsive to the will of our people. He operates by command instead of by consensus. In a second term, he'd be unrestrained by the demands of re-election. And if there's one thing we cannot afford is four years of Barack Obama with no one to answer to."
According to early exit polls, the economy is the top issue for voters in the primary states today, while the ability to defeat President Obama is candidate the quality that matters most to voters.
Speaking to supporters in Ohio, Santorum called Tuesday a "big night" for his campaign.
"This was a big night tonight, lots of states. We're going to win a few, we're going to lose a few, but as it looks right now, we're going to get at least a couple of gold medals and a whole passel full of silver medals," he said. "We went up against enormous odds, not just here in the state of Ohio, where -- who knows how much we were outspent -- but in every state. There wasn't a single state in the list that I just gave you where I spent more money than the people I was able to defeat to win that state. In every case, we overcame the odds."
In both Tennessee and Oklahoma, Santorum did well among the nearly 75 percent of primary voters who identified as evangelical Christians, according to exit polls. He did particularly well among those voters who said it mattered "a great deal" to them that the candidate share their religious beliefs.
In Georgia, which he represented in Congress for 20 years, early exit polls showed Gingrich winning among men, women, and white evangelical voters. He also led among very conservative voters and those who said the economy was their top issue.
Gingrich's victory in Georgia could give the candidate a much-needed boost in momentum after a string of losses in recent nominating contests.
In remarks in Atlanta after the Georgia polls closed Tuesday night, Gingrich made clear that he
"Remember when it was Tim Pawlenty who was going to crowd me out? And remember then when it was Michele Bachmann? And then it was our good friend, Herman Cain the first time? And then, for a brief moment, it was Donald Trump almost," Gingrich told supporters. "And then it was our good friend, Rick Perry, then it was Herman Cain the second time, and now it's Santorum."
He continued: "You just can't quite get across to them: It's all right. There are lots of bunny rabbits that run through. I am the tortoise. I just take one step at a time."
In Virginia, Romney performed well among most demographic groups, including men, women and conservatives. But both Gingrich and Rick Santorum -- who could have posed a threat for Romney in Virginia -- failed to get on the ballot, leaving voters to choose between just Romney and Ron Paul.
Exit polls show Romney with strong support across most demographics in Massachusetts, where he served as governor from 2003 to 2007. He also did well among most demographic groups in Vermont, where he enjoys an advantage due to the state's proximity to Massachusetts.
The ten states in play Tuesday are Ohio, Tennessee, Georgia, Oklahoma, Virginia, North Dakota, Alaska, Massachusetts, Vermont, and Idaho.
All ten states are awarding their delegates proportionately - allocating them based on the outcome in congressional districts, a candidate's percentage of the statewide vote, or a combination of the two (as in Ohio). The lack of "winner take all" contests makes it almost impossible for the remaining GOP presidential hopefuls to accrue enough of the 419 delegates at stake Tuesday to create an aura of true inevitability around their candidacy.