Ohio Lt. Gov. Lee Fisher is ahead of Secretary of State Jennifer Brunner in the Democratic Senate primary, according to a Quinnipiac University poll conducted Feb. 16-21, but half of primary voters are undecided and both Democrats slightly trail former Rep. Rob Portman (R).

Fisher led Brunner 29 percent to 20 percent, with 48 percent undecided in the poll, which surveyed 1,662 voters, including 604 Democrats. 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 Brunner 40 percent to 35 percent. The poll had a 3-point margin of error. The sample of likely Democratic primary voters had a margin of error of 4 points.

Fisher and Brunner are still unknown figures to large swaths of the Democratic electorate even though they were elected statewide in 2006. Half of the 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 a Cincinnati-area House district for a dozen years and has never run statewide, also is not well-known throughout the state.

Both political parties have mediocre public images in the state, the poll found. More respondents rated the Democratic and Republican parties unfavorably than favorably. The “tea party” movement was rated more favorably than unfavorably, though a plurality of those surveyed said they didn’t have enough information to render a firm opinion about it.

The Senate candidates are vying to succeed retiring Sen. George Voinovich (R).