Senator Barack Obama added another victory to his campaign for the Democratic nomination Tuesday, winning the southern state of Mississippi's primary. The 33 delegates at stake will be divided with opponent Senator Hillary Clinton because Democrats divide delegates proportionally according to the vote totals for each candidate.

More than half the Democratic voters in Mississippi are black and around 90 percent of them voted for Barack Obama, the son of a father from Kenya and a white mother. White voters in the state tended to support Hillary Clinton. Many Democrats are troubled by this pattern.

Obama has based his campaign on appealing across racial lines. He won the first contest of this election year on January 3 in Iowa, a state that is around 90 percent white. But since then blacks in every primary or caucus have tended to vote for Obama in large numbers. Less than six months ago, polls showed strong support in the black community for Hillary Clinton, based partially on the accomplishments of her husband, former President Bill Clinton.

Obama has been able to rally support from young voters from all ethnic and racial groups, but older white voters have voted in larger numbers for Clinton. She also has a distinct advantage with women voters.

Clinton is looking for big wins in other states holding contests in the weeks ahead, including such large states as Pennsylvania, Indiana and North Carolina. Her strength with working class voters and women is expected to help her in those states. Since the percentage of black voters in these states is much lower than it is in a state like Mississippi, Obama will need to reinforce his efforts to draw white voters to support him.

One clear advantage Obama enjoys is a more than 100-delegate lead over Clinton, giving him the momentum of a frontrunner. Clinton, on the other hand, hopes her attacks on what she describes as Obama's inexperience will blunt his drive and give her a chance to regain momentum.

Democratic Party leaders view all of this with growing concern, however, since a prolonged contest between these two candidates delays efforts to prepare for the general election and provides Republicans with ammunition to use against the eventual nominee.

Senator John McCain clinched the Republican nomination after winning here in Texas and in three other states on March 4 and has been able to devote time since then to fundraising and preparations for the November election.

Complicating the Democratic race further is the possibility that contests in Florida and Michigan may be repeated. Party officials had taken delegates away from those states after they violated party rules by moving their primaries up on the calendar.

The governors of those states are now demanding that their citizens be represented, so both states are planning to re-do their contests in June. But even after those contests, it is likely that neither candidate will have the 2,025 delegates needed to win the nomination, so the race could continue right up to the national Democratic convention in Denver in late August.