JACKSON, Miss. -- Mississippi Democrats are deciding the last in a series of presidential contests between Barack Obama and Hillary Rodham Clinton before the two rivals settle in for a six-week battle to win Pennsylvania.

Mississippi's large black electorate in Tuesday's voting makes it fertile ground for Obama, who has swept the other Deep South states and has pulled huge margins among black voters. Clinton, the New York senator and former first lady, campaigned in the state last week, but by Monday was in Pennsylvania, where the primary is April 22.

Obama, the first-term senator from Illinois, spent the day in Mississippi, drawing enthusiastic crowds in Columbus and Jackson, the capital. At stake are 33 delegates and another chance for Obama to ease the sting of last week's losses to Clinton in primaries in Ohio, Texas and Rhode Island.

Mississippi's delegates will be divvied proportionally between Clinton and Obama, although if Obama's lead in state polls holds through the ballot counts, he should be able to add at least 17 delegates to his count. Obama leads Clinton in the race to 2,025 delegates -- the number needed to clinch the Democratic nomination -- by 106 delegates so far.

Clinton, who has had difficulty winning in heavily black, southern states, is focusing her campaign Tuesday on more friendly territory by campaigning in Pennsylvania, where she has a governor on her side and favorable demographics.

With Clinton's camp saying she has little chance in Mississippi, the campaigning here focused largely on national issues.

Obama used his Monday morning visit to Columbus to try to squelch speculation that he might accept the vice president's slot on a ticket headed by Clinton. He noted that he has won more delegates, states and votes than Clinton.

"I don't know how somebody who is in second place is offering the vice presidency to the person who is first place," Obama said, drawing cheers and a lengthy standing ovation from about 1,700 people. He added: "I am not running for vice president. "I am running for president of the United States of America."

Later, at a rally in Jackson with 9,000 people, Obama painted Clinton as part of the Washington establishment whose time has come and gone.

The nation does not need "the same old folks doing the same old things, talking the same old stuff," he said, essentially lumping Clinton with President Bush and Republican candidate John McCain.

He accused Clinton's campaign of leaking a photograph of him wearing traditional African garments, including a turban, during a visit to Africa. That was "straight out of the Republican playbook," Obama said. "That's not real change."

Clinton has said she is not aware of anyone on her staff leaking the photo.

For her part, Clinton had moved on to Pennsylvania, where she held a rally in Scranton and carefully sidestepped questions about the sex scandal threatening the political career of Eliot Spitzer, her home state governor and political ally.

"I don't have any comment on that," she said when asked about reports that Spitzer allegedly paid for sex with a high-priced call girl at a Washington hotel. "Obviously, I am sending my best wishes and thoughts to the governor and to his family," Clinton said.

Obama's two Mississippi events drew heavily black audiences that cheered him unabashedly.

"I'm here because of the electricity, the energy that seems to form around Barack Obama," truck driver Jasper Clark, 53, said in an interview before the Jackson rally. "It inspired me, and it's been a while since I've been inspired politically."

Clark said Clinton "is a nice person," but among his friends and acquaintances, "I'd say it's an 8 to 2 ratio" for Obama.