Sen. Sherrod Brown (D-Ohio) continues to lead all potential opponents in his re-election race, according to the most recent Quinnipiac University survey.

Former Ohio Secretary of State Ken Blackwell (R), who has yet to announce a final decision about a bid, performs the best against Brown, but he still trails the first-term Senator by double digits, 35 percent to 44 percent.

State Treasurer Josh Mandel (R), who has filed his paperwork to run for the seat, trails Brown by an even larger margin, 31 percent to 45 percent.

Brown leads former state Sen. Kevin Coughlin (R), who has also expressed interest in the seat, 44 percent to 28 percent.

Blackwell also performed the best in a hypothetical GOP primary matchup, receiving 33 percent over Mandel, who got 17 percent, and Coughlin, who got 5 percent. However, a large portion of GOP primary voters, 43 percent, are still undecided about whom they would pick for the GOP nomination.

Brown’s job approval rating continues to improve, up 6 points since March to 49 percent in the most recent survey.

Roll Call Politics rates this race Leans Democratic.

Meanwhile, President Barack Obama’s approval rating only improved slightly from a similar survey at the end of March, up 2 points to 49 percent. He’s virtually tied with an unnamed Republican on the ballot, 41 percent to 39 percent.

This survey of 1,379 registered Ohio voters was taken May 10-16 and had a margin of error of 2.6 points.