Missouri Gov. Eric Greitens, a rising Republican star, admitted Wednesday to being involved in an extramarital affair in 2015 just before he was elected governor.

St. Louis CBS affiliate KMOV first reported Greitens’ affair, capping a monthslong investigation, after hearing from the ex-husband of the unnamed woman with whom Greitens was involved. The woman’s former husband had covertly recorded her admitting to the affair prior to their divorce and he had released the footage to the television station.