Romney wins primary hat-trick

Republican Mitt Romney has pulled off a stunning hat-trick, winning the Wisconsin presidential primary on top of victories in Maryland and Washington, US media has projected.

CNN, Fox News and the CBS network all called Wisconsin for Romney, shortly after the polls closed there, as he seeks to consolidate his front-runner status in the race to be the Republican contender in the November elections.

The three-state sweep, especially the win in Wisconsin, handed Romney more ammunition to argue he is the inevitable frontrunner as pressure increases on Rick Santorum to end his campaign.

Wisconsin is a swing state that will factor heavily in the 2012 general election. If Santorum had been able to best current delegate frontrunner Romney there, it would have significantly boosted Santorum's campaign going forward.

With a loss in Wisconsin, Santorum remains significantly behind Romney in delegates, and will have the prospect of no additional wins (save in his home state of Pennsylvania--a must-win) in coming contests for the remainder of April. All of this comes as pressure ramps up for Santorum to bow out.