The United States senator, buoyed by evangelical voters, stunned the billionaire to take an early lead in the Republican race.
President Barack Obama has won a second term in the White House, overcoming deep doubts among voters about his handling of the US economy.
Barack Obama launched aggressive attacks against Mitt Romney on jobs, energy and Libya in their second debate as he tried to reclaim momentum.
An aggressive Mitt Romney has taken the fight to Barack Obama and has breathed new life into his struggling campaign with a solid debate performance.
The Democratic Party has officially nominated US President Barack Obama as its candidate for the November 6 election to face Republican Mitt Romney.
Democrats are set to launch their case for Barack Obama's re-election at his nominating convention, looking to draw a sharp contrast with Mitt Romney.
Republican Rick Santorum has won two crucial Deep South primaries, taking control of the conservative wing and dealing a setback to Newt Gingrich.
Many US Republicans may have growing concerns about their presidential front-runner Mitt Romney but no one is pushing the panic button -- yet.
Voters in Iowa open a gruelling presidential race on Tuesday, with polls showing Mitt Romney battling Ron Paul for a momentum-generating win.
Michele Bachmann won the Iowa straw poll on Saturday in the first big test of the 2012 Republican presidential campaign.