WASHINGTON -- Democratic Sen. Barack Obama has gained ground on Sen. Hillary Rodham Clinton in Pennsylvania by drawing more support from men and younger voters, according to presidential polls in the state.

The New York senator is ahead in the state 50 percent to 41 percent, according to a Quinnipiac University poll released Wednesday, but her lead has steadily eroded from 16 points in mid-February and 12 points in mid-March in the same survey.

Clinton still leads, largely because of her dominance of white voters.

Clinton trails Obama in the national popular vote and among delegates to the party's August convention. She wants a strong win in Pennsylvania's April 22 primary to demonstrate she remains a viable candidate and to continue her victories in general election swing states.

She is expected to do well because the state has large numbers of voters who typically support her, including older people, whites, and those without a college education. The Illinois senator would like to trim her margin as much as possible.

Since mid-February in Pennsylvania, Obama has gone from trailing Clinton among men by 10 percentage points to running even. He now leads among people under age 45 by 9 points, reversing an 11-point deficit.

Clinton leads in the state among people without college degrees, but what was a 29-point margin in February is now 19 points.

She has a 25-point lead among whites and almost as big a margin with women, which have changed little since February.

Exit polls of Democratic voters in other state primaries show that Clinton leads nationally among whites, who make up 86 percent of Pennsylvania's population, about 6 points above the national average. She is also ahead with women.

Obama leads nationally among men and younger voters, while Clinton does better with those who have not finished college.

The poll was taken during a time when both candidates were campaigning in Pennsylvania, including a prolonged bus tour by Obama. In the middle of the survey period, Obama was endorsed by the state's popular Democratic senator, Bob Casey, but the poll showed no real difference in voters' preferences just before and after the endorsement.

The Quinnipiac poll was conducted from March 24-31. It involved telephone interviews with 1,549 likely Democratic voters, for whom the margin of sampling error was plus or minus 2.5 percentage points.