Question: Who was a member of the IO theater and the host of a CBS talk program? 

Context paragraphs:
Amber Ruffin: Amber Ruffin is an African-American comedian from Omaha, Nebraska.  She has been a writer for "Late Night with Seth Meyers" since 2014.  When she joined the show, she became the first black woman to write for a late-night network talk show in the United States.  In addition to "Late Night", Ruffin writes on the Comedy Central show "Detroiters" and is a regular narrator on another Comedy Central show, "Drunk History".  She is also a member of RobotDown, a sketch comedy troupe, and a former performer at Boom Chicago, iO Theater, and The Second City.  As of September 2016, she was working on a then-untitled single-camera comedy show as its co-executive producer.  In 2017, she was nominated for, but did not win, a Writers Guild of America award in the category "Comedy/Variety (Including Talk) Series".

IO Theater: iO, or iO Chicago, (formerly known as "ImprovOlympic") is an improv theater and training center in central Chicago, with a branch in Los Angeles called iO West.  The theater both teaches and hosts performances of improvisational comedy.  It was founded in 1981 by the late Del Close and Charna Halpern.  The theater has many notable alumni, including Amy Poehler and Stephen Colbert.

Susan Messing: Susan Messing (born December 26, 1963) is an American improvisational theatre performer, teacher and author associated with the Annoyance Theater and iO Theater in Chicago.

Stephen Colbert: Stephen Tyrone Colbert ( , ; born May 13, 1964) is an American comedian, television host, actor, and writer.  He is best known for hosting the satirical Comedy Central program "The Colbert Report" from 2005 to 2014, and hosting the CBS talk program "The Late Show with Stephen Colbert" beginning in September 2015.

Miles Stroth: Miles Stroth is an American actor, comedian and teacher.  He worked with Del Close and the iO Theater.

Harold (improvisation): Harold is a structure used in longform improvisational theatre.  Developed by Del Close and brought to fruit through Close's collaboration with Charna Halpern, the Harold has become the signature form of Chicago's iO Theater and the Upright Citizens Brigade Theatre in New York City and Los Angeles.  It is now performed by improv troupes and teams across the world.

Ed Schultz: Edward Andrew "Ed" Schultz (born January 27, 1954) is an American television and radio host, a progressive political commentator and a former sports broadcaster.  Schultz currently hosts a daily primetime weekday show on RT America TV channel based in Washington, D.C., that is part of the RT network.  Schultz has hosted a nationally syndicated podcast, "Ed Schultz News and Commentary", since 2015 and a nightly television show, "News with Ed Schultz", since 2016.  He was the host of "The Ed Show", a weekday news talk program on MSNBC, and "The Ed Schultz Show", a talk radio show, nationally syndicated by Dial Global.  The radio show ended on May 23, 2014, and was replaced by a one-hour podcast.

Bernie Ward: Bernie Ward (born Bernard Vincent Ward on April 5, 1951) is an American former radio personality.  Formerly a radio talk show host with KGO 810 AM in San Francisco, California, Ward served a six-year prison sentence for the online distribution of child pornography.  Ward, once billed by KGO as "The Lion of the Left" and "unabashedly liberal," was the host of the daily news talk program, "The Bernie Ward Show," and the three-hour program, "GodTalk", on Sunday mornings.  In December 2007, Ward was dismissed from KGO following his federal grand jury child pornography indictment.  Subsequently, in a plea bargain with federal prosecutors, Ward admitted to a single felony charge of distributing child pornography and signed an admission of distributing between 15 and 150 images via email.

T. J. Jagodowski: Thomas James "T. J." Jagodowski (born September 2, 1971) is an American comedian, actor, and improvisational performer who lives in Chicago.  He has been a member of The Second City as well as a performer and teacher at iO Theater, formerly known as "Improv Olympic".  He has appeared in movies such as "Stranger Than Fiction", "The Ice Harvest", "No Sleep Till Madison", "Get Hard" and the television show, "Prison Break".  He is most recognizable from the long-running series of improvised Sonic Drive-In commercials featuring himself and Peter Grosz.

Luke Null: Luke Null (born July 7, 1990 in Cincinnati, Ohio) is an American actor, comedian, and singer, who currently works as a cast member on "Saturday Night Live", having joined the show at the start of its forty-third season.  Prior to joining the show, Null was known for performing at the iO Theater in Chicago specializing in musical comedy.  Luke Null is now the second "SNL" cast member born in the 1990s after Pete Davidson (though Null is older than Davidson by three years).

Supporting paragraphs: IO Theater Stephen Colbert
Answer: Stephen Colbert