Chicago mayor Rahm Emanuel will be a guest Monday on \"Late Show with David Letterman\" in New York, CBS announced. It will be his visit to the show. A former U.S. representative from Illinois, he served as White House Chief of Staff to President Barack Obama following Obama\'s election in 2008, a position he resigned in 2010 so he could run in Chicago\'s 2011 mayoral election, which he won. He is featured in the documentary \"The Presidents\' Gatekeepers,\" in which, for the first time, all 20 living White House Chiefs of Staff come together to share their previously untold stories. The documentary spans nine presidential administrations and 50 years. It is to air Sept. 11-12 on the Discovery Channel.