Mandan was best known for his role as Chester Tate, the philandering, embezzling stockbroker husband of Katherine Helmond's character Jessica Tate on the soap-opera parody, which ran from 1977-1981. Throughout his career, he often played snooty white-collar types like the crooked Wall Street broker he played on Soap, including an investment banker on Three's Company and its spin-off Three's a Crowd.
He appeared on over one hundred shows during his TV career, which stretched from 1963 to 2014. Other credits include Sanford and Son, One Day at a Time, Star Trek: Deep Space Nine, ER and Murder, She Wrote. He appeared on The Love Boat six times as six different characters, including as himself on the show's cameo-filled series finale. He was also a frequent guest on game shows like The $25,000 Pyramid.
Mandan was primarily a TV and stage actor, and only appeared in a few movies throughout his career, including The Best Little Whorehouse in Texas and MacArthur. On stage, he made his Broadway debut in 1956 in Speaking of Murder, and acted alongside Lauren Bacall in the original 1970 production of Applause.
He is survived by his wife Sherry.