U.S. Republican presidential candidates Mitt Romney and Rick Santorum are locked in a tight battle for the key battleground state of Ohio, one of the 10 states that held voting contests Tuesday.

More than one-third of the 1,144 delegates needed to win the Republican nomination were up for grabs in the “Super Tuesday” nominating contests, more than all the previous primaries and caucuses combined.

In early results, former U.S. House speaker Newt Gingrich won Georgia, the southeastern state he represented in Congress for two decades. Romney was the projected winner in Vermont, as well as Virginia, a state where only he and U.S. Representative Ron Paul were on the ballot.

Romney won the last five contests leading up to Tuesday and he leads in the delegate count. He hopes to use the Super Tuesday races to establish himself as the inevitable nominee. His main rival, social conservative Santorum, is attempting to regain the momentum that helped him win three states in one day in early February.

Romney also is expected to win Massachusetts, the northeastern state where he once served as governor. Santorum, a former U.S. senator from Pennsylvania, holds an election night party in Ohio. Polls have closed in Ohio, but the race is too close to call.

Romney was confident after casting his ballot in Massachusetts.

“As I said, I'm hoping for a good win here in Massachusetts and what happens elsewhere, I don't know. But I think we'll pick up a lot of delegates and this is a process of gathering enough delegates to become the nominee and I think we're on the track to have that happen.”

On Monday, Santorum and Romney both campaigned in Ohio.

Voters in the state Tuesday expressed their backing of both Santorum…

“Essentially, I think he can beat Obama and I think he's got the answer for the future of America.”

… and Romney.

“I like the guy. He's not necessarily my favorite candidate on all issues, but quite frankly, I think he's the most likely to be able to beat Obama in the general election.”

Tuesday's contests will move Republicans closer to selecting their candidate to face President Barack Obama, a Democrat, in the November election.

Representative Paul, who has yet to win a nominating contest, is hoping to do well Tuesday in the three states holding caucus votes — Alaska, Idaho, and North Dakota.

Oklahoma and Tennessee were the other states holding primaries on Tuesday.

President Obama, whose approval ratings have been gradually improving, told a news conference at the White House that Republican presidential candidates have been resorting to “bluster and big talk” on the threat from Iran.

Three of the candidates promised Tuesday they will not hesitate to use America's military might against Tehran. Santorum, Romney, and Gingrich addressed the American Israel Public Affairs Committee Tuesday.