The top three Republican presidential candidates are focusing efforts on the southern United States Monday, on the eve of two nominating contests.

Polls indicate a close race among Mitt Romney, Rick Santorum and Newt Gingrich in both Alabama and Mississippi. The states are important as candidates seek to win over conservatives and widen their support among the party base. Former U.S. House speaker Gingrich is also looking for a comeback after a win last week in the southern state of Georgia.

Romney, a former Massachusetts governor, is far ahead in the number of delegates needed to secure the Republican Party nomination, but has failed to attract support from working-class voters and religious conservatives, who have been drawn to his main rival, Santorum.

In a boost for Romney, a new Washington Post-ABC News poll shows he leads President Barack Obama in a hypothetical election matchup, 49 to 47 percent. The survey, which has a margin of error of four percentage points, indicates Santorum would have 46 percent support to Mr. Obama's 49 percent.

Romney won Wyoming on Saturday, and six contests last week on Super Tuesday, including in the crucial battleground state of Ohio. Santorum, a former U.S. senator from Pennsylvania, won a caucus in Kansas on Saturday, days after scoring three Super Tuesday wins .

U.S. Representative Ron Paul, who has not won a nominating contest, has single-digit support in Alabama and Mississippi.

The Pacific island state of Hawaii also votes Tuesday.

Candidates are awarded delegates through the primaries and caucuses, and a contender needs 1,144 delegates to win the Republican nomination.

The Republican Party will formally nominate its presidential candidate at its convention in Tampa, Florida, in late August. The nominee will face President Obama, a Democrat, in the November election.