Carson and McMahon retired from The Tonight Show in 1992 , when Jay Leno became host . Johnny Carson retired on May 22 , 1992 , and was replaced by Jay Leno amid controversy . David Letterman not only wanted to move into that earlier time slot from his late night spot after The Tonight Show , but was considered by Carson and others as the natural successor ( despite Leno having been Carson 's permanent guest host for several years ) .