Sen. Sherrod Brown (D-Ohio) still has a double-digit lead over his GOP rival, state Treasurer Josh Mandel, but his lead is narrowing, a new poll showed.

Brown takes 46 percent to Mandel’s 36 in a Quinnipiac University poll released Thursday.

Brown’s 10-point edge is down from a 13-point lead in February and a 15-point margin in January in other Quinnipiac surveys. Other polling by Democratic firm Public Policy Polling has shown a similar trend for Brown.

Men are about equally divided between Mandel and Brown, but Brown holds a 17-point lead over Mandel among women. Independent voters also favor Brown by 18 points, the poll showed.

“As is the case with President Barack Obama’s lead in the White House race, the Democratic margin is made up almost completely of the votes of women,” Quinnipiac pollster Peter A. Brown said in a polling memo. “At this point, Josh Mandel is not very well-known, and he can take some solace in the fact that Brown is not over the magic 50 percent threshold.”

The poll of 1,246 Ohio voters was conducted March 20-26 and had a margin of error of plus or minus 2.8 percentage points.

The Hill rates this race as leaning Democratic.