MILWAUKEE (AP) -- Republican presidential front-runner Mitt Romney urged his party to shift focus to the general election and said President Barack Obama "gets full credit or blame" for the economy. The former Massachusetts governor previewed a look-ahead line of attack even as voters went to the polls Tuesday in GOP primaries in Wisconsin, Maryland and the District of Columbia.
Romney's message served double duty as a subtle push to trailing rival Rick Santorum, who has pledged to continue campaigning against Romney until the front-runner has won the presidential nomination.
"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," Romney said in an interview Tuesday with Fox News. "You have to remember that it was Ross Perot that allowed Bill Clinton to win."
Perot ran as an independent in the 1992 general election, when Clinton defeated President George H.W. Bush.
At the same time, Romney and Obama are trading jabs and acting as though the fall campaign is all but set, though Romney suddenly faces a better organized, better financed campaign backed by the power of the presidency.
"He gets full credit or blame for what's happened in this economy, and what's happened to gasoline prices under his watch, and what's happened to our schools, and what's happened to our military forces," Romney told supporters gathered at a sandwich shop in Waukesha, Wis. "All these things are his responsibility while he's president."
Obama, addressing an annual meeting of The Associated Press on Tuesday, poked at Romney for calling Republican Wisconsin Rep. Paul Ryan's budget "marvelous." He also assailed the Republican Party as extreme.
"I think it'd be marvelous if the Senate were to pick up Paul Ryan's budget and to adopt it and pass it along to the president," Romney told Wisconsin voters in a telephone town hall meeting last Wednesday.
Marvelous, Obama said, "is a word you don't often hear when it comes to describing a budget."
Obama's re-election campaign is also running a new TV ad in six swing states criticizing the former Massachusetts governor by name for the first time - in this case as a backer of "Big Oil" amid high gas prices.
Romney responded Tuesday by accusing the president of trying to shift blame for the bad economy.
"The president put an ad out yesterday, talking about gasoline prices and how high they are. And guess who he blamed? Me!" Romney said after handing out ham, turkey and Italian subs to supporters. "Maybe after I'm president I can take responsibility for things I might have done wrong. But this president doesn't want to take responsibility for his mistakes."
Romney made one campaign stop before an election night party in Milwaukee. He spent the weekend campaigning across Wisconsin, accompanied by Ryan and working to win yet another big industrial state that Santorum was counting on to keep his flagging candidacy alive.
Santorum was spending the day in Texas at private fundraisers for his campaign before heading to his home state of Pennsylvania for an election night party in Mars, just north of Pittsburgh.
Romney has 572 delegates to the Republican National Convention, half the needed 1,144, and is on a pace to clinch the nomination by the end of the primary season in June. Santorum has 272 delegates, Newt Gingrich 135 and Ron Paul 51.
There were 95 delegates at stake in Tuesday's contests, including 42 in Wisconsin, the only one of the three contests Santorum has seriously contested. Romney is expected to do well in Maryland and in the District of Columbia, where Santorum is not on the ballot.
Romney has ignored Santorum the past few days to focus on Obama.
Obama's ad claims that "Mitt Romney's stood with Big Oil - for their tax breaks, attacking higher mileage standards and renewables." The ad is in response to a spot from the American Energy Alliance blaming Obama for rising gas prices.
Romney's campaign, though, is running far behind the president in fundraising, as he's been unable to raise general election money because the primary contest is still going on.
At the end of February, Obama reported $84.7 million in his campaign account compared with Romney's $7.3 million. Obama has more than 530 paid staff compared to roughly 100 for Romney.
But Romney has far outspent his rivals during the nomination fight.
Santorum, who also campaigned in Wisconsin on Monday, said Romney has essentially bought his success by spending more than the competition.
Romney and his allies have spent $53 million on television advertising so far this election cycle compared to $27 million from his three Republican competitors combined, according to data compiled by the media tracking firm SMG Delta.
Santorum's team, having narrowly lost a string of high-profile contests, spent just $9 million.
"With almost unlimited resources, Gov. Romney has not proven to be very effective," Santorum said as he predicted a possible upset in Wisconsin. "The only way he's been successful in winning the primaries is by just bludgeoning his opponents by an overwhelming money advantage - something he's not going to have in the general election."