Mitt Romney tightened his grip on the Republican presidential nomination, sweeping three primaries in Wisconsin, Maryland and Washington, DC, by substantial margins and urged his party to shift focus to the election showdown with President Barack Obama.
The victories enabled Mr Romney to extend his already considerable delegate lead over chief Republican rival Rick Santorum, who flashed defiance in the face of growing pressure to abandon his own candidacy in the name of party unity.
“The right thing for us, I think, is to get a nominee as soon as we can and be able to focus on Barack Obama,” ex-Massachusetts governor Romney told reporters.
Despite the setbacks, Mr Santorum, a former Pennsylvania senator, told supporters in his home state that he does not intend to quit the race.
He vowed to keep battling until Mr Romney is assured of the 1,144 delegates needed to secure the nomination at the party’s national convention in late August in Tampa, Florida.