Gov. Paul LePage has said greed is behind the proposal. The No More Casinos Maine political action committee is opposing the initiative.
Lisa Scott of Horseracing Jobs Fairness said in a statement that the casino proposal will preserve horse racing and provide hundreds of jobs. Scott has contributed $4.2 million to the campaign since 2015.
The plan would only allow a York County casino or slot machine operator license for Scott's brother, Shawn, who sold his $51 million stake in Bangor Raceway more than a decade ago.