By Steve Schifferes
With the two key Democratic primaries of Ohio and Texas projected to have gone to Hillary Clinton, the results suggest the key battleground has become white working class men, who in previous votes had been strongly attracted to Mr Obama.
The majority of under-30s voted for Barack Obama, polls suggest
In Ohio, Hillary Clinton appears to have secured the majority of votes from white men and those earning under $50,000 per year.
Meanwhile in Texas, the former first lady appears to have split the white male vote evenly with Barack Obama.
The greater importance of economic issues in Ohio, a state which is suffering more from the economic slowdown - and is more concerned about the effects of trade on jobs - may have influenced working class voters in that state.
A key factor in Mr Obama's strong showing is his strength among independent voters
Over 80% of Ohio Democratic voters said trade pacts were bad for jobs.
Both candidates have retained their traditional core supporters, with Mr Obama winning independent voters, the well-educated and the young, and Mrs Clinton still winning among women, Latinos, and older voters.
INDEPENDENTS FOR OBAMA
A key factor in Mr Obama's vote has been his strength among independent voters - those who are not registered as Democrats.
Both Ohio and Texas allow independents (and Republicans) to vote in the primaries, and they make up 30% of the electorate in Ohio and 33% in Texas.
Independents voted by 52% to 48% for Mr Obama in Texas, and by 54% to 46% in Ohio.
But in both states, Mrs Clinton won a majority among registered Democrats.
HISPANICS FOR CLINTON
In Texas, 30% of Democratic primary voters were Hispanic (many originally from Mexico), 20% were black - and 50% white.
Mrs Clinton won over the majority of registered Democrats, polls suggest
Mrs Clinton, just as she did in California, won a strong majority of Hispanic voters in Texas, with 63% of Hispanics voting for her.
Mr Obama, however, who made a strong effort to improve his showing here, held her majority among Hispanic independents to 56%, and to 58% among Hispanic men.
Mr Obama won an overwhelming 85% of the black vote in Texas, and 90% in Ohio, carrying the large cities like Cleveland, Houston and Dallas.
YOUNG FOR OBAMA
The age gap in voting has been even bigger than the gender gap.
Young people under 30 have been particularly strong for the Illinois senator.
In Ohio, he won 67% of the vote of those aged 18-29, and in Texas he won 60% - the lower percentage being affected by the large Hispanic vote for Mrs Clinton.
In contrast, when it came to voters over the age of 65, the New York senator won 67% of the votes in Ohio and 64% in Texas.
But older voters were a much more important factor in Ohio - where they made up 23% of the electorate - than in Texas, where they only made up 13%.
WOMEN FOR CLINTON
Mrs Clinton continued to poll more strongly among women than men, winning 53% of the female vote in Texas and 54% in Ohio.
And her candidacy also seems to have boosted turnout among women, with 57% of the Texas Democratic electorate made up of women, and 59% of the Ohio electorate.
However, Senator Clinton's advantage among women has diminished somewhat since the days of her early victories, with Mr Obama particularly making inroads among married women.
This analysis is based on exit polls conducted in Texas and Ohio by Edison Media Research and Mitofsky International on 4 March. The sample size was 1577 Democrats in Ohio and 2009 Democrats in Texas, and the margin of error was +/-2%.