Blackwell, the Ohio secretary of state, was blamed by Democrats for voting problems caused by too few voting machines in the Cleveland area in 2004.
If the projection is correct, Strickland would succeed Republican Gov. Bob Taft.
Earlier Tuesday, Ohio Democrats filed suit to keep 16 polling locations in the Cleveland area open till 9 p.m. EST. The polling places, in Democratic strongholds, opened late.
A federal judge issued the order for the polls to stay open until 9 p.m., WKYC-TV, Cleveland, reported.