Romney greets supporters at Mobile's Whistle Stop Cafe on March 12. (John David Mercer/AP)

Weeks after Santorum overwhelmed Romney in Missouri’s “beauty contest” primary, Romney campaigned in a St. Louis park Tuesday, ignoring his Republican rivals and training his rhetorical fire on President Obama. He accused the president of failing to fix the economy and allowing America’s military superiority to slip.

“I wish as a president he would finally take responsibility for 24 million people out of work or underemployed in this country … for not drilling more oil when he could have … for home values having gone down down down … for the national debt that he has almost doubled,’’ Romney told a standing-room-only crowd of more than 500 people spread out around him in folding chairs on a grassy field.

“It’s time for this president to be held responsible, and because of that responsibility, he’s going to be out of office this coming fall,’’ Romney said to loud cheers, holding a microphone and pacing occasionally. He spoke under a “Romney: Believe in America” banner and next to a jungle-gym.

Just outside the park, a small group of protesters held signs with such messages as “Romney: Mr. 1 percent” and “Greed Power powering People.’’

Romney’s visit comes ahead of Saturday’s Missouri caucuses, and he is scheduled to fly to Kansas City to meet voters at a caucus site late Tuesday afternoon. Last month’s primary was nonbinding, but the caucuses will begin a process in which 52 delegates will be awarded.

While Santorum is considered the favorite Saturday, Romney’s appearance in Missouri’s largest cities indicates that his campaign views the state as part of his strategy to continue amassing delegates. The former Massachusetts governor tends to do better in suburban areas and cities, which could allow him to pick up delegates in Missouri even with a Santorum victory.

His decision to skip Alabama and Mississippi on Tuesday may also be an effort to lower expectations in the two states, where some polls have indicated that Romney could perform better than expected as Santorum and Newt Gingrich split the conservative vote. Romney did not mention the Alabama and Mississippi ballots during his St. Louis appearance.

Missouri is one of three states that on Feb. 7 ignited Santorum’s campaign, which had been sputtering since he narrowly won Iowa. The former Pennsylvania senator had been the only Republican candidate to actively campaign in Missouri. Propelled by support from social conservatives, he captured 55 percent of the vote to Romney’s 25 percent.

Ron Paul came in a distant third, while Gingrich did not qualify for the ballot. Santorum also won Colorado and Minnesota the same night, a sweep that helped him emerge as Romney’s main conservative challenger for the GOP nomination to face Obama in November.

Trying to capitalize on his appeal among evangelical voters, tea party activists and other conservatives, Santorum on Saturday campaigned across Missouri’s conservative southern region. Romney, at the St. Louis rally, stuck almost exclusively to his economic message, though he briefly touched on the controversy over the Obama administration’s attempt to require private insurers, including some Catholic institutions, to provide contraceptives to their employees free of charge.

Romney also offered an extended critique of Obama’s record on the politically sensitive issue of rising gasoline prices. “These gas prices are really crushing a lot of people, people who are really struggling at a time when this president is looking around for someone to blame,” he said. Addressing Obama directly, he added: “Maybe it's related to the fact that you stopped drilling in the Gulf ... that you said we couldn’t get a pipeline in from Canada called Keystone. Those things affect the price of gas.”

Despite his mixed prospects in Missouri, the state has not been inhospitable to the Republican front-runner. Romney captured 29 percent of the vote in Missouri in 2008, finishing only four points behind Sen. John McCain, the Republican nominee.

And Romney, like elsewhere, arrives here with significant establishment support. He has been endorsed by a parade of prominent Republicans from Missouri, including former senator Jim Talent, a close Romney adviser, and Sen. Roy Blunt, who is helping him corral support in Congress. Talent introduced Romney at Tuesday’s rally in St. Louis.

Whether Romney can translate that high-level backing into on-the-ground enthusiasm among Missouri conservatives has yet to be determined.

But Tuesday’s crowd whooped and cheered loudly as he strode into the park, wearing a white shirt and blue jeans, and several voters expressed varying degrees of enthusiasm.

Carol Size, 57, of St. Louis held a sign saying “I’m a conservative and I’m voting for Romney.’’ Swaying to music from Diana Ross and the Supremes that was blasting from a loudspeaker, she said she admired Romney’s health-care reform bill in Massachusetts, which is highly controversial among conservatives.

“It was really gutsy of him to be the first Republican to actually come out and address health care for everyone. He took a lot of flak for it,’’ said Size, who dismissed Santorum as “too socially conservative for me.’’

Diane Gangloss of St. Charles County outside of St. Louis said she agrees with Santorum’s pro-life stance on abortion and on other social issues, but fears “the media will skewer him because of his social conservative views.’’

“I saw what they did to Sarah Palin, and I’m afraid the same thing will happen to Santorum,’’ said Gangloss, who thinks Romney is “the best candidate to beat Obama. He’s a conservative and he has the values and business sense to turn this country around.’’

“There is no perfect candidate,’’ she added.

This post has been updated since it was first published.