New surveys show the Republican presidential field locked in a tight contest for two pivotal Southern primaries, one day before voters hit the polls.

A Public Policy Polling (PPP) survey for Alabama shows Mitt Romney with support from 31 percent of likely GOP voters, edging Newt Gingrich at 30 percent. Rick Santorum is at 29 percent, followed by Ron Paul at 8 percent. The gap between the three leaders of the pack falls within the poll’s 4-point margin of error.

In Mississippi, PPP shows Gingrich with 33 percent support to Romney's 31, trailed by Santorum with 27 percent and Ron Paul with 8.

"About all we know for sure about Tuesday's primaries is that Ron Paul will finish last in them," said PPP President Dean Debnam. "Beyond that it's plausible that any of the candidates could finish between first and third in both Alabama and Mississippi," he added.

Both state surveys show that Gingrich and Santorum are viewed more favorably by voters than is Romney, who has admitted that competing for blue-collar, conservative voters is an “away game” for him.

In Mississippi, PPP's data show Gingrich with a net favorability of 33 points, with a 62 percent favorable and 29 percent unfavorable rating. Santorum has a 32-point net favorability, at 60 percent favorable to 28 percent unfavorable.

Romney, however, lags with only 10 percent net favorability, with 51 percent favorable and 41 percent unfavorable.

Similarly, in Mississippi, Santorum has a 32 percent net favorability, Gingrich 26 percent and Romney 13.

However, the polls suggest Romney has remained competitive in these states because Gingrich and Santorum have split the conservative vote.

In Mississippi, Gingrich and Santorum divided voters who identify themselves as  "very conservative" 35 percent to 32, respectively, leaving Romney with 26 percent.

In Alabama, Romney remains competitive at 24 percent support, with Santorum gaining 37 percent of those voters and Gingrich earning 31 percent.

The two Southern primaries, which vote on Tuesday, provide critical tests for the three candidates leading the GOP field.

Gingrich, who represented Georgia in the House for two decades and has racked up wins in his home state and South Carolina, has staked his candidacy on sweeping the South.

Santorum, who has competed with Gingrich to rally GOP voters as the conservative alternative to Romney, could use a strong showing to boost his contention that the GOP contest is a two-man race between him and presumptive nominee Romney.

For Romney, the Southern swing provides another opportunity to prove he can rally conservative voters who have failed to coalesce behind his candidacy and deliver a knockout blow to his rivals.

Romney’s challengers, though, show no intention of dropping out of the race.

Former House Speaker Newt Gingrich said Sunday he plans to stay in the race until the GOP convention in Tampa, Fla., this summer and predicted he would win in both Southern states. “I think we'll win both,” he said

The PPP surveys were conducted from March 10 to 11. Both polls have a 4-point margin of error.