Voters in the southern state of Mississippi are casting ballots on Tuesday in the state's Democratic Party presidential primary.
Opinion polls show Illinois Senator Barack Obama leading rival Hillary Clinton, although the two are likely to split the state's 33 delegates. Delegates are divided proportionally according to the number of votes each candidate wins.
Obama is fresh from a win Saturday in the Wyoming caucuses and leads Clinton, a New York senator and former first lady, by about 100 delegates in the close battle for their party's nomination.
Clinton and her husband, former President Bill Clinton, have suggested a Clinton-Obama ticket for the general election. But Monday in Mississippi, Obama ridiculed the idea of being her vice president, saying he is running for president, not the second slot. He noted he has won more states, votes and delegates than Clinton.
Both candidates are campaigning today in the next major battleground state, Pennsylvania, which holds its primary April 22nd.