Barack Obama won the Mississippi Democratic primary Tuesday, giving him an expected but vital victory in his effort to fracture the momentum Hillary Clinton picked up with her wins one week earlier.

John McCain won on the GOP side, but the Arizona senator has already locked down the nomination and faced no major rivals. Former candidate Mike Huckabee got about 12 percent of the Republican vote.

Polls consistently showed Obama was favored to win in Mississippi. The state's sizable black electorate -- 37 percent of the state's population, the highest concentration in the nation -- was poised to give him a big boost, as it did in other southern states like Georgia and South Carolina.

Though neither candidate scheduled an election-night rally, both campaigns issued statements on Tuesday's results.

"We congratulate Senator Obama for his win in Mississippi and thank our supporters and volunteers there for their support, hard work, and long hours," Clinton campaign manager Maggie Williams said. "Now we look forward to campaigning in Pennsylvania and around the country as this campaign continues."

"I am grateful to the people of Mississippi for joining the millions of Americans from every corner of the country who have chosen to turn the page on the failed politics of the past and embrace our movement for change," Obama said, emphasizing his campaign theme of change.

"Americans need a president in Washington who will bridge our differences instead of exploit them, take on the lobbyists instead of taking their money and concentrate on fighting for your future instead of their own. That's what I've done over the course of my two decades of public service, and that's the message I'll bring to Americans in the remaining 10 contests left in this nominating process."

FOX News exit polls showed race was a factor for many voters. Nearly half the voters in Tuesday's Democratic primary were black, and nine out of 10 went for Obama, according to exit polls. By contrast, 72 percent of white voters went with Clinton.

A majority of voters said race was not an issue for them, but of those who did, 60 percent went for Obama.

Polls closed in Mississippi after a day of racially charged comments. Obama's campaign called on 1984 vice presidential candidate Geraldine Ferraro, a prominent Clinton supporter, to step down from her position on the Clinton finance committee after she told a California newspaper that Obama was being helped politically by his race.

Obama called the comments "absurd."

But race wasn't the only factor in Mississippi. Obama still held the lead among voters casting their decisions on a range of issues. Of those who picked the economy as their top concern, 54 percent went for Obama and 45 percent went for Clinton.

Sixty-seven percent said Obama inspires them the most about the future of their country, and 61 percent said Obama offers the most detailed plan.

Both candidates campaigned in Mississippi. Former Gov. Ray Mabus campaigned with Obama Monday and Tuesday. Rep. Bennie Thompson, D-Miss., also joined Obama on Tuesday, and said before results came in that the heavily black delta region would go overwhelmingly for the Illinois senator.

Obama won the Wyoming caucuses Saturday, but his campaign was trying to recover from Clinton's victories in the Ohio, Texas and Rhode Island primaries March 4. The wins kept her campaign alive and signaled the Democratic race could drag on through the final contests June 3, and potentially to the August convention.

Both candidates spent their night in Pennsylvania, which is the next big contest on April 22. That followed campaigning by the two in the Keystone State.

Mississippi's primary was the last chance to pick up steam before the Pennsylvania race, which offers 156 delegates. That's the biggest prize left on the primary calendar, and with polls favoring Clinton it poses an opportunity for the New York senator to catch up to Obama in the delegate count. North Carolina votes on May 6 to apportion its 115 pledged delegates.

Obama went into Tuesday's contest with 1,579 delegates, to 1,473 for Clinton. It takes 2,025 to win the nomination. Before Tuesday's vote 602 pledged delegates were left to be allocated. With 28 of Mississippi's 33 delegates allocated, Obama picked up an additional 17 and Clinton 11.

As voters went to the polls in Mississippi, back in Canonsburg, Pa., Bill Clinton told voters just as he did in Ohio and Texas that it's up to them to save his wife's candidacy.

"I think she's got to win a big victory in Pennsylvania," he said. "I think if she does, she can be nominated, but it's up to you."

In Mississippi, turnout was mixed, with the most people showing up in areas that offered both presidential and congressional primaries. Mississippians were voting on two rare open congressional seats.

In some areas, officials said morning rain may have slowed participation.

Mississippi's secretary of state predicted a light to moderate turnout, but with 98 percent of precincts reporting, more than 407,000 people had voted in the Democratic race and about 128,000 Republicans had gone to the polls. That's just under 30 percent of total registered voters.

The Associated Press contributed to this report.