Mitt Romney rolled to a double-digit victory in Washington State’s Republican Presidential caucuses on Saturday night, his fourth triumph in a row and a fresh show of strength in the run-up to 10 campaign contests being held all across America on Tuesday.

The 10 primaries and caucuses coming up on so-called Super Tuesday should shape the Republican race to find a challenger to President Barack Obama.

Mr. Romney said in a statement that his win meant Washington State’s voters “do not want a Washington insider in the White House. They want a conservative businessman who understands the private sector and knows how to get the federal government out of the way so that the economy can once again grow vigorously. ”

Former Pennsylvania Senator Rick Santorum and Texas Representative Ron Paul battled for second place on Saturday in Washington State, while the former Speaker of the House of Representatives, Newt Gingrich, ran a distant fourth.

Returns from caucuses in 60 per cent of Washington State’s precincts showed Mr. Romney with 37 per cent of the vote, while Mr. Paul and Mr. Santorum each had 24 per cent. Mr. Gingrich was drawing 11 per cent.

Mr. Romney’s win was worth at least 12 of the 40 delegates at stake. Mr. Paul and Mr. Santorum each won at least three. The rest remained unallocated, pending final returns.

Mr. Romney, Mr. Santorum and Mr. Gingrich were all campaigning in Ohio the most intensely contested of the States holding nominating contests on Tuesday as the first caucus returns were reported from Washington State. Mr. Paul was in Washington State as the caucuses began, searching for his first victory of the campaign.

The Republican race has shared the political spotlight in the past few days with a controversy in which conservative talk show host Rush Limbaugh called a Georgetown University law student a “slut” and a “prostitute” an issue that the Republican Presidential rivals seemed reluctant to comment on.

Mr. Limbaugh apologised on his website during the evening to the woman, Sandra Fluke, who had spoken out publicly in favour of a requirement for most insurance coverage to include contraception. Mr. Obama called Ms. Fluke on Friday to express his support. Polls show Mr. Obama’s support among women voters on the rise since Republicans made contraception an issue.

The Super Tuesday primaries and caucuses stretch from Vermont to Alaska. But the top showdown is in the Midwestern industrial State of Ohio, an important test for Mr. Romney who has struggled to win over conservatives who make up the party’s base.

Mr. Santorum, a favourite of social conservatives, surged in national and State polls of Republican voters after winning contests in Minnesota, Colorado and Missouri on February 7, 2012. But he has fallen back under a barrage of negative TV ads from Mr. Romney and his supporters. His own lack of campaign organisation has raised questions about his ability to compete against the former Massachusetts Governor over the long haul.

Mr. Romney, the party establishment’s favourite, swept contests in Arizona and his native State of Michigan on Tuesday, giving him momentum heading into the next round of contests.

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