Thousands of Iowa Republicans cast the first ballots of the 2012 presidential contest on Tuesday, with front-runner Mitt Romney locked in a tight race with Rick Santorum and Ron Paul that remains unpredictable because many voters still hadn't settled on a favorite candidate.

On Tuesday night, Republicans will gather in living rooms, high school gymnasiums and local libraries to start the process of picking the party's nominee to challenge President Barack Obama in the Nov 6 election. In each precinct caucus, voters will urge their friends and neighbors to support a preferred candidate.

The caucuses could winnow the seven-candidate field of Republicans seeking the party's nomination.