PASCAGOULA, Miss. (AP) — Seeking to tap into the public's concern over rising gas costs, Mitt Romney on Thursday said President Barack Obama was "in part" to blame for higher prices at the pump.Romney, the front-runner in the Republican presidential field, said Obama has tried to shirk his responsibility for increases in the price of gas, which could threaten to upend some recent improvements in the nation's economy."He says 'it's not my fault,'" Romney said during a campaign stop on Mississippi's Gulf Coast. "This is in part his fault. This is a guy who has slowed down ... the licensing and permitting of offshore rigs, of onshore drilling."Despite Romney's assertions, economists say there's not much a president of either party could do about gasoline prices. The current increases at the pump have been driven by fears of a war with oil-rich Iran and by higher demand in the U.S. as well as in China, India and other quickly growing nations.While the price of gas has stabilized somewhat in recent days, a gallon of regular unleaded is still nearly 50 cents higher than it was at the beginning of the year.Speaking against the backdrop of massive oil rigs in the Port of Pascagoula, Romney renewed his calls for accelerating drilling permits and pledged to approve the Keystone XL pipeline that would bring oil from the U.S. to Canada. Approving the project, Romney said, should be a "no-brainer."Obama rejected the pipeline earlier this year, saying there wasn't enough time to properly study the project ahead of the deadline forced upon him by Republican congressional lawmakers. On Thursday, the Democratic-controlled Senate blocked another Republican bid to speed approval of the pipeline, which would stretch from Canada to Texas.The president says he supports an "all-of-the-above" energy strategy that includes oil, gas, wind and solar power. U.S. oil production has increased during Obama's term, though Republicans say that is due in part to the policies of his predecessor, George W. Bush.Following a solid, if uninspiring performance, on Super Tuesday, Romney has a comfortable lead in the Republican delegate race as the GOP contest moves to the Deep South. Romney was spending two days campaigning in Alabama and Mississippi, both states holding primaries on Tuesday.Seeking to boost his standing with Southern voters, the former Massachusetts governor said he was turning into an "unofficial Southerner" with the help of a campaign staffer who hails from Mississippi."I'm learning to say 'y'all' and I like grits. Strange things are happening to me," Romney said jokingly.Romney picked up the endorsement Thursday of Mississippi's Republican Gov. Phil Bryant, who appeared with Romney at the Port of Pascagoula and pledged to campaign for him every day in the lead-up to the state's primary. Bryant said he was hopeful for a strong Romney finish in Mississippi."I think he's going to do well. People are going to embrace him," Bryant said.