A look at four polls conducted in Ohio ahead of the state's Democratic primary.
Quinnipiac University poll
Hillary Rodham Clinton, 49 percent
Barack Obama, 45 percent
Obama has cut Clinton's 11-percentage-point lead from a Feb. 25 poll, making gains with men and black voters. The gender gap looms large in Ohio, with women backing Clinton 55 percent to 39 percent. She also maintains an advantage with lower income voters and older voters.
The Quinnipiac University Poll was conducted Feb. 27-March 2 and involved interviews with 799 likely Democratic primary voters in Ohio. The margin of sampling error was plus or minus 3.5 percentage points.
The (Cleveland) Plain Dealer poll
Hillary Rodham Clinton, 47 percent
Barack Obama, 43 percent
Clinton leads Obama among women (53 percent to 38 percent) and voters older than 50 (54 percent to 36 percent), while Obama holds almost identical leads among men and those younger than 50.
When asked what the most important issue is when voting, 52 percent said the economy. Forty-three percent of respondents said they favored Clinton's position on the economy, compared to 27 percent for Obama.
Fifty-nine percent said they disapprove of the North American Free Trade Agreement, and 52 percent said Clinton and Obama's positions on NAFTA were basically the same.
The (Cleveland) Plain Dealer/Mason-Dixon poll was conducted from Feb. 27-29 and involved telephone interviews with 625 likely Democratic voters in Ohio. The margin of sampling error was plus or minus 4 percentage points.
Boston's Suffolk University poll
Hillary Rodham Clinton, 52 percent
Barack Obama, 40 percent
Undecided, 4 percent
Refused to respond, 4 percent
Clinton leads among women, older voters, those who have already cast their ballots and those in the northeast Ohio, Columbus/Southeast and Toledo/Northwest areas. Obama is stronger among younger voters, African-Americans, independents and people from other parties, and those in the Cincinnati/Dayton area of the state.
The poll by the Political Research Center at Boston's Suffolk University was conducted March 1-2 among 400 Ohio residents. The margin of error was plus or minus 4 percentage points.
"The Ohio Poll" by the University of Cincinnati
Hillary Rodham Clinton, 51 percent
Barack Obama, 42 percent
The poll shows Clinton maintaining her lead in Ohio. A Feb. 25 survey by the same group showed her ahead by 8-percentage points. The poll shows that 6 percent of Democratic voters plan to support John Edwards, who has dropped out of the race.
The Ohio Poll sponsored by the University of Cincinnati was conducted Feb. 28-March 2. It involved interviews with 624 likely Democratic voters and had a margin of sampling error of plus or minus 4 percentage points.