A late surge in support for Mitt Romney has raised expectations that the Republican frontrunner can quash doubts about his candidacy on Super Tuesday, the biggest day of the 2012 nomination race.

However, even as he begins to win more support among conservative voters, there are signs that Barack Obama is pulling away from Mr Romney and the other Republican contenders in head-to-head match-ups with the president. Of the 10 states up for grabs today, Mr Romney is well placed to win at least five and possibly more, according to the latest polls, which would increase the pressure on other candidates to drop out.

Mr Romney needs to force his main rivals, Rick Santorum and Newt Gingrich, out of the race as quickly as possible, as the prolonged contest is draining his campaign of money and the support of independent voters.