SWEEPS DAY 12!! Obama Says Goodbye To LETTERMAN!! And LETTERMAN Primetime!! Herc’s Monday TV Talkback!! Read the full article on AICN David Letterman is leaving “Late Night” May 20 and CBS at 9:30 p.m tonight airs the 90-minute primetime special “David Letterman: A Life On Television.” Then President Obama tonight makes his final appearance on “The Late Show With David Letterman.” Kevin Williamson’s “Stalker” narrowly defeated Kevin Williamson’s “The Following” in the 9 p.m.