Barack Obama handily defeated Hillary Rodham Clinton in Mississippi's Democratic primary on Tuesday and captured the Deep South's last presidential contest before the rivals' showdown in Pennsylvania next month.
"What we have tried to do is steadily make sure that in each state we are making the case about the need for change," Obama said from Chicago.
John McCain, who has clinched the Republican nomination, easily won his primary and was in New York raising money.
Obama's victory follows his win in Saturday's Wyoming caucuses, but does little to decide the most competitive Democratic contest in more than two decades. "This race keeps on going," said pollster Mark Mellman, who is neutral in the race.
Neither Democrat is likely to capture the 2,025 delegates needed to win the nomination solely through the 10 remaining contests. Elected and party leaders known as "super delegates" could decide the nominee at the party's August national convention.
"The math is clear: At the end of the day, it is the super delegates who are likely to make the decision," Mellman said.
Obama has won in Alabama, Georgia and other Southern states where blacks are a large part of the electorate. In Mississippi, which has the nation's highest percentage of black residents, nine of 10 black voters picked Obama, surveys of voters as they left polling places showed. Clinton won seven of 10 white voters, exit polls showed.
Both candidates campaigned in the state, but spent much of the day in Pennsylvania with an eye toward its April 22 primary and 158 pledged delegates. Mississippi allocates 33 delegates.
Clinton did not speak publicly after Tuesday's vote, but told Mississippi voters earlier "I'm for you." Campaign manager Maggie Williams said Clinton congratulated Obama and looks "forward to campaigning in Pennsylvania and around this country as this campaign continues."
Clinton has a double-digit poll lead in Pennsylvania, a bellwether in general elections. She needs a big win there to advance her claim that she is best positioned to capture swing states in November, said G. Terry Madonna, a political scientist at Franklin & Marshall College in Lancaster, Pa.
If Obama wins, "there will be enormous pressure for (Clinton) to end her campaign," he said. "If she wins, the battle of the titans continues."
Gabriel Bobbette, a Hattiesburg, Miss., maintenance worker, who is black, said race did not influence his vote for Obama. "He's capable of doing the job," Bobbette said. Joseph Barker, a Georgia Pacific worker in Petal, Miss., picked Clinton. "You know what you are getting when you get a Clinton," Barker said.
Contributing: Associated Press; Hattiesburg (Miss.) American