Mitt Romney swept primaries in Maryland, the District of Columbia and Wisconsin on Tuesday, taking another decisive step toward the 2012 battle he and President Barack Obama have been circling for months.
Romney was halfway to the 1,144 delegates needed to secure the Republican presidential nomination before polls closed and was poised to pick up the bulk of D.C.'s 19 delegates, Maryland's 37 and Wisconsin's 42.
Romney and Obama engaged earlier Tuesday in a tense back and forth, and Romney maintained the general election focus when he took the victory stage in Wisconsin.
"Under Barack Obama," he said, "America hasn't been working." He portrayed Obama as a big-government advocate bent on "transforming" the country.
"It's opportunity, not a check from government that has always driven America and defined us as Americans," Romney said.
He made a populist dig at the president over high gas prices and looked forward to closing out the primary later this month.
"Tonight, I'm asking the good people of Pennsylvania, New York, Rhode Island, Delaware and Connecticut to join me," he said referring to the states that vote April 24. "Join me in the next step toward that destination of Nov. 6, when across America we can give a sigh of relief and know that the promise of America has been kept."
The primary is now in the fourth month of voting and even as Romney moved closer to his goal, three other candidates continue to hang on. Newt Gingrich and Ron Paul have been dismissed as serious challengers, but Rick Santorum has not relented in a attacking the front-runner.
A defiant Santorum told supporters in Mars, Pa., the state he represented in Washington for 16 years, that it was only "halftime."
"Who's ready to charge out of Pennsylvania for a strong second half?" Santorum asked, invoking the state's revolutionary history and working-class grit.
He focused his remarks heavily on health care, a vulnerability for Romney due to the similarities between the plan he oversaw in Massachusetts and the federal law Democrats now embrace as Obamacare. (Romney repeated his call Tuesday to repeal the law.)
"If we're going to win this race, we can't have little differences between our nominee and President Obama. We have to have clear contrasting colors," Santorum said, repeatedly referring to Romney as a "moderate" and comparing himself to Ronald Reagan.
Santorum signaled he was banking not just on Pennsylvania but Texas, which holds its primary May 29 and has a whopping 155 delegates.
Still, Romney's night only adds to pressure on Santorum to withdraw.
The night's big prize and closest contest was Wisconsin.
Exit polls showed Romney was helped by the smaller number of evangelical voters, a group that has fueled Santorum's wins in other states, and fewer voters who identify themselves as very conservative.
Romney and his allies badly want to end the primary campaign, which is sapping resources and continues to expose doubts about his appeal to the GOP base.
The former Massachusetts governor received a string of high-profile endorsements in the last two weeks — including Florida U.S. Sen. Marco Rubio and Wisconsin U.S. Rep. Paul Ryan — most of which focused on his inevitability as the nominee rather than his conservative credentials.
Wisconsin voters agreed overwhelmingly: Exit polls showed more than 80 percent of Republicans who cast ballots expect Romney to be the nominee.
Earlier in the day, Romney urged the party to get on with the general election.
"The right thing for us, I think, is to get a nominee as soon as we can and be able to focus on Barack Obama," he said in an interview Tuesday with Fox News. "You have to remember that it was Ross Perot that allowed Bill Clinton to win."
Obama fired his own salvo Tuesday. He ridiculed Romney for backing the House GOP budget plan, spearheaded by Ryan, which Democrats say is extreme.
The president, appearing at a meeting of Associated Press reporters and editors in Washington, specifically mentioned Romney for the first time in a public speech and poked fun at him for saying it would be "marvelous" for the Senate to adopt the Ryan budget plan. Marvelous, Obama said, "is a word you don't often hear when it comes to describing a budget." Obama cast the budget as "nothing but thinly veiled social Darwinism."
The Obama campaign this week launched a TV ad in Florida and a handful of other key election states that tries to tie Romney to Big Oil and pointed out that domestic oil production is at an eight-year high, a claim PolitiFact.com deemed "Mostly True."
The Republican National Committee said the ad was proof Obama is "panicked" over high gasoline prices. A pro-Obama political committee began running a similar ad in Florida this week, too.
Gingrich, Paul hang on
The GOP primary race has been a two-man struggle for more than a month, but Gingrich and Paul have refused to drop out.
Gingrich has scaled back his campaign and said he's working on securing undeclared delegates to head off Romney at the convention in Tampa.
Paul has been ignored by the news media for weeks, failing to turn the enthusiasm among young voters into primary wins.
"We're still making a lot of the noise in the grass roots," campaign spokesman Jesse Benton insisted in an interview. Paul plans visits to 20 college campuses, mostly in California and Texas, over the next month. "He's in until he's the nominee," Benton added, "or another candidate gets 1,144 delegates."
Meanwhile, Romney's finance team is gearing up a series of fundraisers focused on the general election. "We're shifting gears right now," said St. Petersburg developer Mel Sembler. "Everybody understands Romney is our nominee. It's over."
Alex Leary can be reached at email@example.com. Follow him on Twitter @learyreports.