The president’s campaign, which also seems convinced Mr Obama will face Mr Romney in the November election, is running television ads that try to link the former Massachusetts governor to big oil companies as high petrol prices threaten to influence already stressed voters.
“Mitt Romney’s stood with Big Oil – for their tax breaks, attacking higher mileage standards and renewable energy sources,” an ad says. It is a response to an ad from Crossroads, a Republican super political action committee that is expected to spend millions of dollars attacking Mr Obama this year.
With Republican primaries in Wisconsin, Maryland and Washington, DC, Mr Romney is set to hold one campaign event before an election night party in Wisconsin. He spent the weekend campaigning there, working to win yet another big industrial state that chief rival Rick Santorum was counting on to keep his fading candidacy alive.
“Take the next step here in Wisconsin,” Mr Romney urged supporters. “I need you to go out and vote. Get your friends.”
Mr Romney has ignored the conservative Mr Santorum for the past few days as he has focused on Mr Obama, telling supporters that the president “takes his political inspiration from the capitals of Europe”. The often-used Republican line of attack is meant to imply an opponent is elitist and not in touch with the American mainstream.
Mr Obama, meanwhile, was to issue a broad attack on Republicans, criticising their budget plan.
Mr Romney has 572 Republican National Convention delegates, half of the 1,144 needed to win the Republican nomination. Mr Santorum has 272. Newt Gingrich, the former speaker of the House of Representatives, has 135 and Ron Paul 51.