MILWAUKEE (AP) -- Mitt Romney is turning away from his primary opponents and toward Democratic President Barack Obama after sweeping three more Republican contests.

The likely GOP nominee was set Wednesday to take the same Washington stage that the president had used a day earlier to criticize Romney in a speech to newspaper editors in Washington. The former Massachusetts governor planned to address an audience of the Newspaper Association of America and the American Society of News Editors, a day after Obama spoke to the annual meeting of The Associated Press.

"There is a basic choice before us," Romney said Tuesday night as he spoke to cheering supporters in Milwaukee. "Our different visions for America are the product of our values and our life experiences."

Romney's victories in Wisconsin, Maryland and the District of Columbia widened his delegate lead and all but handed him the title of presumptive Republican nominee. Despite pressure to leave the race, rival Rick Santorum vowed to fight on, urging voters in the next-up Pennsylvania primary to vote for "someone whose views are forged in steel, not on an Etch A Sketch."

Romney didn't mention Santorum on Tuesday night. Instead, Romney sought to cast Obama as an "out of touch" liberal whose personal background is hostile to a free economy.

His remarks came just hours after Obama delivered a combative campaign speech in Washington, where he attacked House Republicans' budget plan as "thinly veiled social Darwinism" that "is antithetical to our entire history as a land of opportunity and upward mobility for everybody who's willing to work for it."

Obama called it "a prescription for decline."

After his speech Wednesday, Romney planned to head to a campaign event in the Philadelphia suburbs. He was to campaign in the state Thursday as well. Obama planned to attend an Easter prayer breakfast at the White House.

For Romney, the end of the contested primary campaign could hardly come soon enough.

"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 told radio host Sean Hannity on Tuesday. "I think we've had, as of tonight, we will have had almost 35 or more state or territorial contests for the nomination. Maybe it's time to get going."

Obama has gained in the polls in recent months, particularly among women, as Republicans vie among themselves for support from a conservative party electorate. Santorum has devoted more time to social concerns - including birth control - than Romney, who has generally stayed focused on economic issues.

Surveys indicate Americans are growing more optimistic about the overall state of the economy. Unemployment has fallen in recent months, but it is still at a relatively high 8.3 percent of the work force.

Already, the early outlines of a general election ad war are visible. Obama's re-election campaign is airing commercials in a half-dozen battleground states that accuse Romney of siding with Big Oil "for their tax breaks, attacking higher mileage standards and renewables."

The ads are a rapid response to $3 million in commercials aired by an outside group, American Energy Alliance, blaming the president for rising gasoline prices.

In his campaign for the Republican nomination, Romney has collected endorsements from former President George H.W. Bush; Florida Sen. Marco Rubio, a tea party favorite; and Rep. Paul Ryan of Wisconsin, author of a conservative budget that Republicans pushed through the House last week.

Romney won at least 83 delegates in the three races Tuesday, with 6 yet to be allocated.

That pushed his total to 655 of the 1,144 needed to clinch the nomination. Santorum has 278 delegates, Newt Gingrich 135 and Ron Paul 51.

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