Among Democratic voters, Sen. Hillary Clinton, D-N.Y., has a 13-point margin among respondents with a high school education or less. Sen. Barak Obama, D-Ill., leads among other groups, including a 34-point margin among Democrats with post-graduate educations, the Princeton, N.J., polling group said.

Black Democrats strongly favor Obama regardless of educational level, poll results indicated. Among non-Hispanic, white Democrats, the difference in support was large among those with post-graduate educations, and widens among those with high school educations or less.

Among white Democrats with high school educations or less, Clinton is favored over Obama by roughly a 2-to-1 margin. By a reduced margin, she is favored among white Democrats with some college.

Besides being favored overall among college graduates, Obama holds a 2-to-1 edge among white Democrats with post-graduate educations -- reflecting the opposite results among Democrats with high school educations or less.

Results are based on telephone interviews with 2,859 Democratic voters conducted April 1-7. The sampling error is plus or minus 2 percentage points.