MILWAUKEE -

Presidential candidate Mitt Romney swept a trio of GOP primaries Tuesday, coasting to wins over chief rival Rick Santorum in Wisconsin, Maryland and Washington, D.C.

Romney assailed President Barack Obama as an "out of touch" liberal Tuesday night as he looked past the three primary victories and toward the fall's general election.

"Out of touch liberals like Barack Obama say they want a strong economy, but they really don't like businesses very much," the former Massachusetts governor told supporters gathered in the Grain Exchange in downtown Milwaukee as he celebrated wins in Wisconsin, Maryland and the District of Columbia.

"Years of flying around on Air Force One, surrounded by an adoring staff of true believers telling you what a great job you are doing, well, that might be enough to make you a little out of touch," he said.

Romney's decisive win over rival Rick Santorum in Wisconsin moves him closer to becoming the presumptive nominee to run against Obama in a general election contest that's all but begun.

Obama's re-election campaign is running an ad in six swing states attacking Romney. The president jabbed at Romney on Tuesday during a speech to the annual meeting of The Associated Press. And Romney is starting to push Santorum to the sidelines, telling conservative radio host Sean Hannity that "it's time to get going" in the race against Obama.

Romney on Tuesday cast the election as a "basic choice" between what he called Obama's "government-centered society" and the "opportunity society" he says he would pursue as president.

"I don't want to transform America. I want to restore the values of economic freedom and opportunity and limited government that have made this nation the leader it is," Romney said.

He painted a dire portrait of the state of the country, saying that more Americans have lost their jobs under Obama than under any other president since the Depression. Romney blamed Obama for the economic recession that began under Republican President George W. Bush.

"These last few years have been difficult, made worse by mistakes and failures of leadership," Romney said.

The front-runner was set to press forward with the still-ongoing nomination fight with stops in Pennsylvania on Wednesday and Thursday -- the primary there, in Santorum's home state, is April 24.

But he pushed his rivals toward the exits. "I want to have our nominee start raising money, start organizing a national campaign and focus on President Obama and his agenda because this is time for us to start focusing on him rather than standing and focusing on one another in these primary contests," he said.

The three-week lull before contests in late April promises a flurry of behind-the-scenes general election activity -- including hiring staff and fundraising -- as well as campaigning in the northeast. Pennsylvania is also a key battleground state in the fall.

"The White House is engaging more," said Romney strategist Stuart Stevens. "They've already been obsessed with Mitt Romney."

Stevens called the general election "an MRI of Obama's record," a rejoinder to Obama strategist David Axelrod's assertion that presidential campaigns are "MRIs of the soul."

Romney is still on pace to rack up in June the delegates he needs to win the nomination at the Republican National Convention. On Tuesday, he won at least 74 delegates in the three races, with 21 yet to be allocated.

That pushed his total to 646 of the 1,144 needed to clinch the nomination. Santorum has 272 delegates, Gingrich 135 and Paul 51.

Santorum was not in Wisconsin to watch the election results, instead choosing to campaign in his home state of Pennsylvania.

Santorum said the race for the Republican nomination is only halfway over.

"Pennsylvania and half the other people in this country have yet to be heard," Santorum told supporters. "We're going to go out and campaign here and across this nation and make sure their voices are heard in the next three months."

Santorum said he would stay in the race until the Texas primary on May 29. He said he fully expects to win in Texas.

Meanwhile, Ron Paul held a town hall in California on Tuesday, while Newt Gingrich had no official campaign appearances.

Gingrich said he isn't leaving the party's presidential race and is vowing to continue all the way to the nominating convention.

Gingrich said Tuesday he is committed to carrying the banner of bold conservative colors all the way to Tampa to ensure, in his words, "the Republican Party never abandons the timeless conservative principles."

With only two primary victories and Romney on pace to win the nomination in June -- if not before -- Gingrich faces an uphill fight. He lost all three of Tuesday's primaries, contests in Wisconsin, Maryland and the District of Columbia.