Romney leads in Wisconsin, picks up more endorsements

GOP presidential front-runner Mitt Romney picked up another key endorsement as the latest polls show him leading by up to 10 points in Tuesday's Wisconsin primary.

Wisconsin Sen. Ron Johnson gave his support to the former Massachusetts governor Sunday, USA Today reported.

That follows key endorsements from House Budget Committee Chairman Paul Ryan and former President George H.W. Bush, as well as Sen. Jim DeMint of South Carolina and former Florida Gov. Jeb Bush as the GOP appeared to begin coalescing around Romney as the party's nominee, CNN reported.

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Four statewide polls in Wisconsin taken since last week give Romney leads ranging from 5 to 10 percentage points, according to USA Today.

His chief remaining rival, former Pennsylvania senator Rick Santorum, said on NBC's "Meet the Press" that he would stay in the race at least through his home-state primary on April 24.

"We have to win Pennsylvania, and we're going to win Pennsylvania. There's no doubt about that," he told "Meet the Press."

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Santorum downplayed Romney's endorsements in an interview with Fox News on Sunday, calling them a sign "the establishment is getting nervous" and comparing his rival to party moderate John McCain.

"We came up with someone who … wasn't able to win," he told Fox News. "We don't need to repeat that again. We don't need to bail out and not have the best candidate to take Barack Obama on in the fall."