Former Secretary of State Ken Blackwell continues to hold a substantial lead over all of the other potential candidates in the GOP primary to challenge Sen. Sherrod Brown (D), according to a new poll.

Blackwell received 49 percent of the vote, state Treasurer Josh Mandel received 16 percent, and former state Sen. Kevin Coughlin received 3 percent in a new survey from the Democratic firm Public Policy Polling. Thirty-one percent of voters in the poll said they were undecided.

Blackwell has not yet announced whether he will run for the Senate seat, but he told Roll Call recently he’ll make the final call soon. Mandel and Coughlin have both filed paperwork to run for the seat, but Mandel — a favorite of national Republican groups — has yet to officially announce his campaign.

The PPP survey took the opinion of 400 usual Ohio Republican primary voters from May 19 to 22 and had a margin of error of 4.9 points.