MONTGOMERY, Ala. (AP) -- Mitt Romney hoped to seal his status as the Republican presidential front-runner with a thus-far-elusive victory in the Deep South, a region that has been slow to embrace the former Massachusetts governor.

A pair of closely fought primaries Tuesday in Alabama and Mississippi also could render a possible final verdict on Newt Gingrich's Southern-focused candidacy and give Rick Santorum the two-man race he's sought against Romney.

Santorum picked up a vote from Alabama Gov. Robert Bentley, who had not publicly endorsed the former Pennsylvania senator. Bentley's spokesman said the governor traveled to his hometown of Tuscaloosa to vote for Santorum, whom he considers "the most conservative candidate in the Republican presidential race."

With polls showing an unexpectedly tight race in the conservative bellwether states, Romney stopped in Alabama on Monday -- a clear indication he was eyeing a potential win there.

Romney appeared with Southern comedian Jeff Foxworthy and poked fun at his own lack of hunting skills, saying he hoped to set out with an Alabama friend who "can actually show me which end of the rifle to point."

Battling anew to be Romney's main conservative challenger, Gingrich and Santorum both spoke at an energy forum in Biloxi, Miss., then took questions on religion in public life at a presidential forum in Birmingham, Ala. They sharply criticized President Barack Obama, with Santorum labeling the president's foreign policy "pathetic" and Gingrich taunting Obama as "President Algae" for speaking of research that one day would allow oil and gas to be developed from algae.

Gingrich has focused his campaign in recent weeks on rising gas prices, promising to bring the price to $2.50 per gallon if elected.

The Southern showdown came as new polling showed a steep drop in Obama's approval ratings amid escalating prices at the pump and renewed turbulence in the Middle East.

A Washington Post-ABC News poll found that 46 percent of those surveyed approve of the way Obama is handling the job, while 50 percent disapprove. A New York Times/CBS poll found 41 percent approval and 47 percent disapproval.

A win in either Mississippi or Alabama would be an important breakthrough for Romney, easing concerns that the Harvard-educated Northeasterner cannot win the party's most conservative and evangelical voters. Romney did not plan to be in the South during voting and was already looking ahead to contests in Missouri on Saturday and Puerto Rico on Sunday.

Santorum, who has angled to go head to head with Romney, pressed his argument that Gingrich should consider stepping aside.

"People of Mississippi and Alabama want a conservative," he told reporters in Biloxi. "If they want a conservative nominee for sure, they can do that by lining up behind us and making this race clearly a two-person race outside of the South."

Santorum planned to watch returns from Louisiana, which holds its primary March 24. He was heading to Puerto Rico on Wednesday and Thursday to campaign for Sunday's island primary.

While Gingrich insists he'll remain in the race until the Republican National Convention in August, his campaign's survival essentially rested on winning both Tuesday contests. The former House speaker has pursued an all-Southern strategy, but he has won only South Carolina and Georgia, the latter the state he represented in Congress for 20 years.

Gingrich planned several appearances in Alabama on Tuesday, including remarks to a local Chamber of Commerce. A visit to the Birmingham Zoo was canceled because of the weather.

He seemed to draw new energy from an enthusiastic crowd at the Birmingham forum which gave him repeated standing ovations as he derided Obama for apologizing to Afghan President Hamid Karzai after American troops burned Islamic holy books, including some Qurans.

"He believes in apologizing to those who kill our young men and women. I will never apologize," Gingrich said to applause and cheers of "Newt! Newt! Newt!"

All three candidates were receiving support from well-heeled independent groups known as super PACs that were helping to finance television ads, automated phone calls and direct mail in the two states.

A fourth candidate, Texas Rep. Ron Paul, was not competing actively in the two contests.

Hawaii also was holding a primary Tuesday, but none of the GOP hopefuls campaigned there.

Romney has more delegates than his rivals combined, and is amassing them at a rate that puts him on track to clinch control of nomination before the convention opens in late August. The Associated Press tally shows him with 454 of the 1,144 delegates needed to win the nomination. Santorum has 217, Gingrich 107 and Paul 47.

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Associated Press writers David Espo in Washington and Philip Elliott in Montgomery, Ala., contributed to this report.

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