December 17, 2008 Former Colorado Attorney General and U.S. Senator Ken Salazar (D) nominated as Secretary of the Interior by President Obama.
January 3, 2009 Denver Public Schools superintendent Michael Bennet (D) appointed to fill Salazar’s U.S. Senate seat through the 2010 mid-term election by Colorado Governor Bill Ritter (D).
January 20, 2009 Ken Salazar approved as Secretary of the Interior.
January 22, 2009 Michael Bennet sworn in as junior U.S. Senator from Colorado. At age 44, Bennet is the youngest member of the U.S. Senate. Mark Udall (D) becomes Senior Senator from Colorado after being in office only 16 days. Udall and Bennet have the least seniority of any Senate delegation in the U.S.
April 15, 2009 Aurora City Councilman Ryan Frazier (R) announces his candidacy for Bennet’s Senate seat in 2010.
October 28, 2009 update: Frazier pulls out of race.
April 28, 2009 Weld County District Attorney Ken Buck (R) announces his candidacy.
May 7, 2009 Denver businessman Cleve Tidwell (R) announces his candidacy.
July 31, 2009 Crested Butte attorney Luke Korkowski (R) announces his candidacy.
October 2009 update: Korkowski pulls out of race.
Summer 2009 Penrose patent attorney Steven Barton (R) announces his candidacy. August 15, 2009 Former Colorado Lieutenant Governor and former executive director of the Colorado Department of Health and Environment Jane Norton (R) announces her candidacy.
August 17, 2009 National Republican Senatorial Committee registers domain names for former Colorado Lieutenant Governor Jane Norton to use for a website.
August 28, 2009 The Denver Post reports Weld County District Attorney Ken Buck (R) is considering leaving the race.
August 31, 2009 Weld County District Attorney Ken Buck announces he will remain in the race.
August 31, 2009 Former state Senator Tom Wiens (R) of Douglas County e-mails a letter to raise money to explore launching a full campaign for the open U.S. Senate seat. September 16, 2009 Andrew Romanoff (D), former three-term member and Speaker of the Colorado House of Representatives announces his candidacy, the first Democrat to challenge Bennet to a primary.
September 17, 2009 President Obama endorses Bennet in White House statement.
November 5, 2009 Former state Senator Tom Wiens (R) announces his candidacy.