Birmingham, Alabama:  Mitt Romney is working to seal his status as the Republican presidential front-runner with a thus-far-elusive victory in the Deep South.

Closely fought primaries in Alabama and Louisiana offer the former Massachusetts governor a key opportunity in a region that has been slow to embrace him. Tuesday's primaries were also poised to render a possible final verdict on Newt Gingrich's Southern-focused candidacy.

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

Romney campaigned 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 Rick Santorum both spoke at an energy forum in Mississippi and took questions on religion in public life at a presidential forum in Birmingham, Alabama.

They took sharp aim at President Barack Obama, with Santorum labelling the president's foreign policy "pathetic" and Gingrich taunting Obama as "President Algae" for an energy speech in which Obama spoke of research that would allow oil and gas to be developed from algae one day.

Gingrich has focused his campaign in recent weeks on rising petrol prices, promising to bring the price to $2.50 (Dh9.18) 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 per cent of those surveyed approve the way the president is handling his job, and 50 per cent disapprove. A New York Times/CBS poll found 41 per cent approval, and 47 per cent 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.