Sen. swept to an easy victory in the Democratic presidential primaries in Virginia and Maryland chiefly on the strength of his support among African-American voters, according to CBS News exit polls in these two states. He was also aided by a small boost in turnout among young voters - another core support group.
Despite talk that Obama might be gaining momentum by picking up support from John Edwards' supporters, and that the nature of the contest between him and Sen. might be changing, the exit polls demonstrate that his strength today came more from the make-up of these primary states than from any fundamental shift in this two-person contest.
Race and gender have been playing influential roles in the Democratic primary elections this year, and the contests in Maryland and Virginia were no different. As he has in all of the primaries to date, Obama won the vote of African-Americans overwhelmingly. He beat Clinton 88 percent to 11 percent in Maryland, and 89 percent to 11 percent in Virginia, among black voters.
Clinton, in contrast, won her primary support group - white women. She won 54 percent of white women in Virginia's Democratic primary, and 55 percent in Maryland's.
Beyond strong support among African-Americans, Obama also benefited from increased voter turnout - but among young voters, not black voters. Black voters made up roughly the same percentage of the electorates this year as they did in the 2004 primaries. For example, in 2004 African-American voters were 33 percent of the Democratic primary electorate in Virginia. Today they were 30 percent.
Young people were extra motivated to vote this year, presumably by Obama. In 2004 17 - 29 year-olds made up only 8 percent of both Maryland's and Virginia's Democratic primary electorates. Today, however, they made up 14 percent of each state's electorate. Among these young voters Obama won handily. He beat Clinton by 50 points among Virginia's young voters, and by 39 points in Maryland.
Another pattern that has become familiar this year also held up in the Potomac states - the desire for change, and the choice of Obama as the agent for it. Over half - 56 percent of Virginia Democratic primary voters said they most wanted a candidate who could bring about needed change, as did 57 percent of Maryland voters. Obama was the overwhelming choice among these voters - winning 82 percent to 17 percent among Virginians seeking change, and 84 to 14 percent in Maryland.
Only 21 percent of Virginia voters and 21 percent of Maryland's Democrats were looking for Clinton's strong suit - experience. Clinton won more than nine in ten voters in each state who said they most wanted a candidate with the right experience to be president.
The Nature of the Contest
Despite Obama's sweeping victories in these states, the exit polls demonstrate that the fundamental nature of the race between Obama and Clinton remains unchanged, even given upheavals caused by other candidates dropping out of the race, or contests won and lost. In this two-person race, each candidate has a relatively solid base of support on which they can count, possibly indicating a long fight for the nomination.
In general, Clinton and Obama have been dividing the white vote by gender. When the race is at near parity - such as in New Hampshire - Clinton wins white women (46 to 33 percent in New Hampshire) and Obama wins white men (38 to 30 percent in New Hampshire).
Additionally, Obama has consistently won among black voters of all demographic profiles, while Clinton has won among Latinos. As a result, Obama has won primary states with sizable African-American populations (such as today's) and Clinton has won strongly Latino states (Arizona and California).
Finally, Clinton's most solid support has been among the Democratic base - white voters of lower income and education, and those who consider themselves to be true Democrats. In contrast, Obama has consistently sewn up the support of white, well-off, better educated, independent-minded primary voters.
Little of this was different in today's contests. Obama and Clinton split the white vote by gender, as they have in the past, and Obama overwhelmingly won the African-American vote.
Even beyond race and gender, the familiar patterns of support remain. Among white Democratic primary voters with household incomes of less than $50,000 a year in Virginia and Maryland, Clinton won 62% and 52 percent of the vote respectively. In comparison, among those making over $50,000 in Virginia, Obama won with 55 percent of the vote. He and Clinton split the vote among white, higher income Maryland voters.
Among white primary voters with no college degrees, Clinton won 59 percent of the vote in Virginia and 58 percent of the vote in Maryland. Obama won 57 percent and 50 percent of Virginia's and Maryland's college-educated whites.
Among those white voters who self-identify as Democrats, Clinton won 54 percent of the vote in Maryland and 57 percent in Virginia. Obama easily won white independents in these two contests with 57 percent and 63 percent respectively.
Finally, while pundits have speculated about where John Edwards' supporters have gone, and some have argued that Obama's current success is indicative of his having won them over, the exit polls demonstrate that in Maryland and Virginia, if these supporters went anywhere, it was to Clinton. In Virginia, white voters who made up their minds in the past week, the time span covering Edwards' withdrawal, divided evenly among Clinton and Obama, 49 percent to 50 percent respectively. And among white Maryland voters who chose their candidate in the same time period, 54 percent chose Clinton while 42 percent voted for Obama.
Overall, the persistence of each candidate's vote coalition demonstrates that while the nature of the primary states, and individual elections, change each week, the overall nature of this two-person race remains remarkably stable.
The exit polls were conducted for CBS News and the National Election Pool by Edison Media Research and Mitofsky International. The Maryland Democratic primary exit poll contains 1,324 voters, and the Virginia Democratic primary exit poll contains 1,245 voters interviewed as they left the polling place. The margin of error for each survey is + 3 percentage points.
Monika L. McDermott is assistant professor of political science at the University of Connecticut, where she teaches and conducts research on voting behavior and public opinion. Before joining the University of Connecticut, McDermott worked in election polling for CBS News and the Los Angeles Times. She holds a Ph.D. in political science from the University of California, Los Angeles.