Calls for Romney rivals to drop out Mitt Romney's decisive win in the Illinois primary marks the beginning of the end for the drawn-out competition for the Republican presidential nomination, analysts said on Wednesday, and increases the pressure on his rivals to drop out of the race. But Rick Santorum, the social conservative who has been riding an anti-Romney wave, is showing no signs of bowing out and is instead heading towards a victory in Louisiana on Saturday. After Louisiana, however, Mr Romney is now heading into friendlier territory, with states including Maryland, Connecticut and New York set to vote over the next month. "Mitt Romney is close to finishing off his rivals for the Republican presidential nomination, talk of a brokered GOP convention in August, and the prospect of a new candidate suddenly entering the contest," said Fred Barnes of the Weekly Standard, the conservative magazine. Republicans have been concerned there would be no clear winner by the time the party holds its nominating convention at the end of August, raising fears of a bloodbath. "This would be a political hat trick once it happens, and the moment is likely to come quite soon, now that Romney has won an overwhelming victory in the Illinois primary," Mr Barnes wrote in a blog post on Wednesday. Mr Romney won the large Midwestern state by a 12-point margin over Mr Santorum with 47 per cent of the vote. He also won at least 41 of the 54 convention delegates up for grabs. A candidate needs 1,144 delegates to secure the nomination and Mr Romney is now more than halfway there, with 563, according to the Associated Press, and the only candidate with the mathematical possibility of winning. Mr Santorum has 263 delegates and would need to win 70 per cent of all remaining delegates in order to clinch the nomination - an extremely tall order. Despite wins in Mississippi and Alabama last week, Mr Santorum has been losing momentum as it becomes increasingly apparent that Mr Romney will clinch the nomination. Meanwhile, Newt Gingrich, the former House speaker who slumped into single digits to finish in fourth place in Illinois, trails with 135 and libertarian Ron Paul has 50. A former private equity executive and Massachusetts governor, Mr Romney had long been considered the favourite for the nomination but has struggled to pull ahead, with each of his rivals enjoying periods as the "anti-Romney" candidate. But with three consecutive wins in the Midwest - in Michigan, Ohio and Illinois - he has shown some ability to win over the heartland. Exit polls from Illinois showed that Mr Romney fared better than previously with groups he has struggled to win over, such as married women, while Mr Santorum suffered from the relatively low proportion of evangelical Christians. With Mr Romney ahead in the delegate count, even conservative groups who had criticised him are beginning to rally behind him. FreedomWorks, the organisation behind the Tea Party movement, has decided to drop its opposition to his candidacy. "It is a statistical fact that the numbers favour Mitt Romney," Russ Walker, FreedomWorks" vice-president, told the Washington Times. We are dedicated to defeating Obama and electing a conservative Senate that will help Romney repeal Obamacare [healthcare reform] and address the nation's economic and spending challenges. Mr Romney sought to use his resounding victory to call an end to the primary battle, which has been longer, more expensive and more bitter than many Republicans envisaged. It's time to say this word: enough! Mr Romney told cheering supporters at a victory rally in Schaumburg, Illinois, on Tuesday night, seeking to reframe the contest as being him versus Barack Obama. We know our future is brighter than these troubled times . . . We deserve a president who believes in us," Mr Romney said. But Mr Santorum portrayed himself as the only one who would fight for freedom. We don't need a manager," he said at a campaign rally in Gettysburg, Pennsylvania, the site of President Abraham Lincoln's civil war address. His remarks were a sideswipe at Mr Romney, who has touted his business experience as making him best placed for the presidency. But voting across the state was subdued, with Chicago election officials predicting the city's lowest turnout ever for a presidential primary.