[2] He was elected to the State Senate in 1970, defeating Republican incumbent Arthur Piasecki, and was the Democratic caucus leader 1989 through 2010.
[3] In the 1980s, Mellow was under investigation by the FBI for allegedly taking kickback from Mount Airy Lodge, however charges were never filed.
He was also known to be good friends with the former owner of Mount Airy Lodge, Louis DeNaples, who had suspected ties to the Bufalino crime family.
[11] In March 2012, Mellow agreed to plead guilty to charges of conspiracy to commit mail fraud and filing a false income tax return.
[12] Mellow formally pleaded guilty on May 9, 2012, to a conspiracy charge related to using Senate staff members to do political work and filing a false tax return.
He gave the same answer when asked if he understood he was pleading guilty to a felony and that it would affect his ability to vote and hold a political office.