Washington, Mar 13 (IANS): Ahead of Tuesday's tough Republican primaries in Alabama and Mississippi in deep South to pick up the party candidate to challenge President Barack Obama, leading contender Mitt Romney remained at a slight advantage over his two rivals.

In a poll by Public Policy Polling in Mississippi's Republican primary, former Massachusetts governor Mitt Romney led former speaker Newt Gingrich, 34 percent to 32 percent, which was within the poll's margin of error. Another poll in Alabama's primary showed Gingrich at 34 percent to 31 percent for Romney, a gap also within the sampling error.

Romney's closest rival former senator Rick Santorum trailed in both polls -- 10 points behind Gingrich in Alabama and 12 points behind Romney in Mississippi. The fourth Republican candidate, House member Ron Paul, has not campaigned in either state.

Gingrich and Santorum are competing to become the lone conservative survivor in the race against the more moderate Romney for the Republican presidential nomination.

According to CNN's estimate, Romney has 458 delegates, compared with 203 for Santorum, 118 for Gingrich and 66 for Paul. A candidate needs 1,144 delegates at the Republican convention to secure the party nomination. Despite his delegate lead, Romney has been unable to attract broad support among the Republican's conservative base.

In addition to the Alabama and Mississippi primaries, Hawaii and American Samoa hold caucuses Tuesday.

Romney spoke about the tight race in Alabama Monday, telling voters, "This could be an election that comes down to a very small margin between the three people running here most aggressively."