Romney sweeps three more primaries in Wisconsin.

Republican presidential candidate Mitt Romney scored a high-profile victory Tuesday night in the politically-charged state of Wisconsin.

Romney is also the winner in the Maryland and District of Columbia primaries. At this point in the race, the former Massachusetts governor has secured more than half the delegates needed to win the GOP nomination outright and the increased momentum that could help him eclipse his main GOP rival, Rick Santorum.

With nearly all precincts reporting in Wisconsin, Romney has 43 percent of the vote, Santorum has 38 percent of the vote, Ron Paul has 12 percent, and Newt Gingrich has 6 percent. In Maryland, with all precincts reporting, Romney is winning 49 percent of the vote, while Rick Santorum is carrying 29 percent. In Washington, with all 143 precincts reporting, Romney won 70 percent of the vote, Paul won 12 percent and Gingrich has 11 percent. Santorum failed to get on the ballot in Washington.

The primary in Wisconsin was the main event Tuesday, giving one candidate the opportunity to win in a large, politically active state that's sure to be competitive in the general election.

Wisconsin's recent political environment has been intense: The state saw a string of Tea Party victories in the 2010 election, politically divisive recalls last summer, and will hold a recall vote on Republican Gov. Scott Walker this summer. Romney is aiming to deliver a final blow to his main rival Rick Santorum's campaign in Wisconsin, while Santorum is striving to expand his voter base and perform well ahead of the April 24 primary in his home state of Pennsylvania.

CBS News exit polling out of Wisconsin shows Romney winning across voting blocs: He is winning among college graduates and those without a college degree, as well as among those making more than $50,000 and less than $50,000. He also has the most votes from both men and women. Romney is tied with Santorum among those who describe themselves as "very conservative" and wins among conservatives overall.

Romney is winning among voters who say they support the Tea Party movement, though Santorum has the most support so far from Wisconsin voters who say they oppose the movement. Santorum has also bested Romney among evangelical voters so far.

Exit polling also revealed that Romney supporters in Wisconsin supported his candidacy more strongly than his backers in previous primaries, such as Illinois.

As voters appear to become more comfortable with Romney, the GOP establishment also is coalescing around his candidacy as well. Romney has shored up the support of several high-profile Republicans at this point -- including Wisconsin Rep. Paul Ryan and Wisconsin Sen. Ron Johnson -- with some saying a longer primary could be detrimental to the GOP in the general election.

For his part, Romney on Tuesday night appeared ready to move into the general election, focusing his attacks on President Obama rather than his Republican rivals. "A lot of Americans have given up on the President but they haven't thought about giving up," he said in Milwaukee, Wisconsin. "Not on themselves. Not on each other. And not on America."

Santorum, meanwhile, gave a forceful speech from Mars, Pennsylvania, where he said the primary has only reached "half time."

"And who's ready to charge out of the locker room in Pennsylvania for a strong second half?" he asked the crowd.

Santorum's last, best hope for a comeback would be in his home state of Pennsylvania, which votes on April 24. There's some evidence, however, that his support could be waning even there: A recent poll out of Pennsylvania showed Santorum with just a narrow, two-point lead. Ahead of Santorum's "victory" rally in Mars, there were no local television reporters present, CBS News' Dean Reynolds reports -- a first for a primary or caucus night.
With his projected victories Tuesday night, CBS News now estimates Romney has at least 630 delegates -- more than half of the 1,144 delegates needed to win the GOP nomination outright. Santorum has 246 delegates, Gingrich has 128 and Paul has 45.

There were a total of 92 delegates at stake Tuesday, with 39 coming from Wisconsin, 37 from Maryland, and 16 from Washington. The Maryland and D.C. primaries were closed to Republicans while Wisconsin held an open primary.