U.S. presidential candidate Barack Obama is favored in Tuesday's Democratic Party primary in the state of Mississippi.

The Illinois senator is in a tight race against rival Hillary Clinton.

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.

The Clinton campaign has suggested the two form a ticket headed by Clinton. But at a campaign stop Monday in Mississippi, Obama ridiculed the idea, saying he is running for president not vice president. 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 22.

Republican Senator John McCain has won the needed number of delegates for his party's nomination. The veteran Arizona lawmaker, who was campaigning Tuesday morning in Missouri, has focused his sights on the November general election in which he will face off with the Democratic Party nominee.

Some information for this report was provided by AFP and AP.