U.S. Republican presidential candidates are busy campaigning throughout the day Monday, as they head into the "Super Tuesday" nominating contests in 10 states.
Former Massachusetts governor Mitt Romney is locked in a tight battle with Rick Santorum, a former U.S. senator, in the closely watched contest in Ohio.
A new opinion poll shows the Ohio race is too close to call. The Quinnipiac University survey shows Romney has gained momentum since last month, and now has 34 percent of likely Republican primary voters, three points ahead of Santorum. In February, Santorum led in Ohio.
The contests Tuesday will move Republicans closer to selecting their candidate to face President Barack Obama, a Democrat, in the November election.
Super Tuesday features a diverse set of states with 419 delegates at stake - roughly equal to the total number number of delegates contested so far. A candidate needs 1,144 delegates to secure the nomination.
Romney leads the delegate count so far, and hopes to continue his momentum from recent wins into Tuesday.
Meanwhile, former House speaker Newt Gingrich is making national media appearances, while also holding events in Tennessee. He is confident of a win in Georgia, the southeastern state he represented in Congress for two decades, and where polls show he has a large lead.
Ron Paul, a U.S. representative from Texas, is campaigning in Idaho, after making stops Sunday in Alaska.
The other states taking part in Super Tuesday are Massachusetts, North Dakota, Oklahoma, Vermont and Virginia. Romney is expected to do well in Massachusetts, where he was governor from 2003 to 2007, and in the neighboring state of Vermont.
Some information for this report was provided by AP, AFP and Reuters.