Candidates set for Super Tuesday
Republican presidential hopefuls are preparing for the crucial Super Tuesday primary and caucus votes in 10 US states.
Mitt Romney is the front-runner to become the party's nominee to face president Barack Obama in the presidential poll in November.
His progress will depend largely on the vote in the bellwether state of Ohio, where polls show the former Massachusetts governor and Rick Santorum, a former Pennsylvania senator, in a virtual tie.
Mr Romney, who beat Mr Santorum in a close contest in Michigan last week, hopes to continue his winning trend, having won four consecutive contests including Saturday's Washington state caucuses.
At stake in the 10 states that cast ballots on Super Tuesday are 419 delegates to the party's August national convention, by far the most of any day in the primary season. A candidate must amass at least 1,144 to win the nomination.
The states going to the polls are Georgia, Idaho, Massachusetts, North Dakota, Ohio, Oklahoma, Tennessee, Vermont and Virginia, along with Alaska's two-week-long caucuses. Going into the balloting, Mr Romney leads with 203 delegates from previous contests, Mr Santorum has 92, Newt Gingrich has 33 and Ron Paul has 25.
Mr Romney, despite his lead, faces persistent scepticism among conservative voters who dislike his past moderate record.
Mr Obama, meanwhile, is seeing his poll numbers rise in tandem with signs that the struggling US economy may finally be on a course towards sustained recovery.
He has also been helped considerably by the Republicans having been driven off their economic message by a detour into a nasty debate over whether religious-affiliated institutions such as hospitals and universities should be required to offer health insurance coverage for contraceptives.
The issue seems certain to deepen the concerns of many women voters who - along with the broad spectrum of all independents - are likely to determine the ultimate outcome in the November election. Polls show women are already turning back to Mr Obama.