WASHINGTON (CNN) -- Sen. Barack Obama and former New York City Mayor Rudy Giuliani top their respective presidential fields in support from young voters, according to a new poll conducted by Harvard University's Institute of Politics.

Over one-third (35 percent) of young likely Democratic voters support Obama's presidential bid, the poll reveals.  The Illinois Democrat is followed by Sen. Hillary Clinton, D-New York, with 29 percent and former North Carolina Sen. John Edwards with nine percent.

On the GOP side, 31 percent of young voters give the nod to Giuliani, 18 percent support Sen. John McCain, R-Arizona, and eight percent back former Gov. Mitt Romney, R-Massachusetts.

The poll also indicates that 31 percent of young people approve of President Bush's job performance. A CNN/Opinion Research Corporation poll released Monday showed that 36 percent of all Americans approve of the job the president is doing.

The Harvard poll, conducted by Harris Interactive, surveyed almost 3,000 U.S. citizens from ages 18 to 24. About half of the respondents were enrolled in four-year colleges and universities; the other half were not. The survey has a margin of error of plus or minus 3 percent.