Cassidy was back on the Great White Way playing songwriter Jeff Barry in the ill-fated revue cum musical "Leader of the Pack". He fared better on the small screen as a manipulative West Point cadet who crosses the wrong person in "Dress Gray" (NBC, 1986) and co-starring alongside legend Loretta Young in the vehicle that marked her return to acting, the sentimental but not maudlin holiday movie "Christmas Eve" (NBC, 1986). Cassidy next stepped into Patrick Swayze's dancing shoes, assuming the role of Johnny Castle in the TV spin-off of "Dirty Dancing" (CBS, 1988), which didn't last too long on the air.
After a decade as a mostly journeyman player, Cassidy enjoyed one of his best roles as the closeted soap opera actor hired to portray daytime's first homosexual character in "Longtime Companion" (1990), which chronicled the effects of the AIDS epidemic on a group of gay men in NYC. He then landed the stage role of a strolling balladeer who acts as a chorus in the controversial stage musical "Assassins" (1990-91), written by John Weidman and Stephen Sondheim. For the remainder of the decade, Cassidy divided his time between the occasional film part ("I'll Do Anything" 1994), guest roles on TV (notably a recurring part on ABC's "Lois & Clark: The New Adventures of Superman" in 1997) and stage work ("Company" in 1993, an L.A. production of "Assassins" in 1995, this time as John Wilkes Booth). In 1999, he and his second wife, singer-dancer Melissa Hurley Cassidy, toured with Deborah Gibson in the popular Andrew Lloyd Webber-Tim Rice musical "Joseph and the Amazing Technicolor Dreamcoat" (a role his half-brother David played on Broadway in the 1980s). The fall of the following year, Cassidy, now sporting a beard, returned to Broadway paired stage with Cheryl Ladd in the revival of "Annie Get Your Gun".