Mitt Romney has won the Maryland, Wisconsin and the District of Columbia Republican primaries in the US, boosting his momentum as frontrunner in the race for his party's presidential nomination.
"We have won a great victory tonight in our campaign to restore the promise of America," Romney said in his victory speech on Tuesday.
"The right thing for us, I think, is to get a nominee as soon as we can and be able to focus on [President] Barack Obama."
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The former Massachusetts governor comfortably defeated his Republican rivals Rick Santorum, Newt Gingrich and Ron Paul in all three states.
In Wisconsin, Romney won 48 per cent of the vote compared to Santorum's 38 per cent. In Disctrict of Columbia, Romney won 70 per cent. With 75 per cent of the tally counted in Maryland, Romney won 49 per cent compared to Santorum's 29 per cent.
Romney's success in all three primaries underscores his growing strength and is likely to increase appeals from party leaders for Republicans to rally behind him, despite deep reservations expressed by many grassroots conservatives.
Bill Schneider, a resident fellow at the Third Way think tank, said after Tuesday's victories that Romney's nomination was "just about a sure thing".
Schneider told Al Jazeera that Romney was "very likely" to get the majority of delegates needed, "but probably not until sometime in late May or early June, which is why Rick Santorum is hanging on."
"Until (Romney) wins that majority, Santorum believes, and I think this is a delusion, but he believes there is a chance that Romney will not go into (August's Republican National) Convention with a certain first ballot victory and that it will be an open convention that could turn to Rick Santorum."
Peaked 'too early'
Santorum, a former Pennsylvania senator who had emerged as the standard bearer for many among the party's conservative base, admitted defeat in the three contests, but has refused to bow out of the race.
"Pennsylvania and half the other people in this country have yet to be heard. And we are going to go out and campaign here and across this nation to make sure that their voices are heard in the next few months," he said.
Santorum had hoped to break Romney's momentum in Wisconsin, a Midwestern heartland state, but Wednesday's result bore out a late surge that had put Romney in front in the polls.
Al Jazeera’s John Hendren reporting from Madison, Wisconsin, said that despite promising poll numbers for Santorum early on, Romney’s victories had not come as a surprise.
"It would’ve been a surprise two months ago, but that was back when Rick Santorum was ahead in the polls," Hendren said. "But, as he's done in so many states, he peaked too early here."
"Santorum has to regain the confidence, not only of his backers, but of his financial backers and of Republicans at large."
The wins give Romney 98 more delegates, putting him well over half of the 1,144 needed to clinch the nomination at the party convention in August.
They also set the tone for the next big date on the campaign calendar, April 24, when six states hold Republican presidential contests.
Romney leads in five of them and plans to make an aggressive push in the sixth, Santorum's home state of Pennsylvania.
A Quinnipiac University poll released on Tuesday showed Santorum ahead of Romney there by 41 to 35 per cent.