Lt. Gov. Lee Fisher leads Ohio Secretary of State Jennifer Brunner in the Democratic primary for the state’s open Senate seat, but half of primary voters are undecided and both Democrats slightly trail former Rep. Rob Portman (R), according to a new Quinnipiac University poll.

Quinnipiac surveyed 1,662 voters, including 604 Democrats. The poll had a margin of error of 2.4 points.

Conducted Feb. 16-21, the poll found Fisher leading Brunner 29 percent to 20 percent, with 48 percent undecided. Two lesser-known Democrats also are running in the May 4 primary.

Portman, who is unopposed in the Republican primary, led Fisher 40 percent to 37 percent and led Brunner 40 percent to 35 percent.

Fisher and Brunner are still unknown figures to large swaths of the Democratic electorate even though they were elected statewide in 2006. Half of Democrats surveyed said they didn’t know enough about Fisher to have either a favorable or unfavorable opinion of him. Sixty percent of Democrats said the same about Brunner.

Portman, who represented the Cincinnati area in the House for a dozen years before serving as director of the Office of Management and Budget, has never run statewide. He’s not well-known throughout the state either, with 66 percent of those surveyed telling pollsters they didn’t know enough about him to rate his favorability.