FRANKFORT, Ky. (AP) -- Democratic Chairman Dan Logsdon said Williams' father-in-law, Russell Springs businessman Terry Stephens, has been the only contributor to the Republican group, Restoring America, that is airing ads supporting Williams and attacking Democratic Governor Steve Beshear.
Logsdon said that suggests coordination, leading him to ask for an immediate investigation.
Williams and independent candidate Gatewood Galbraith are running against Beshear in the November 8 general election. Polls show Williams is the leading challenger among the two.
Williams campaign chairman Donald Storm said Logsdon's "unfounded and untrue" allegation shows the race is tightening.