| Election Name: | 2008 United States Senate election in Colorado |
| Country: | Colorado |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 2002 United States Senate election in Colorado |
| Previous Year: | 2002 |
| Next Election: | 2014 United States Senate election in Colorado |
| Next Year: | 2014 |
| Election Date: | November 4, 2008 |
| Image1: | File:MarkUdall-Senate Portrait.jpg |
| Nominee1: | Mark Udall |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 1,231,049 |
| Percentage1: | 52.80% |
| Nominee2: | Bob Schaffer |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 990,784 |
| Percentage2: | 42.49% |
| Map Size: | 250px |
| U.S. Senator | |
| Before Election: | Wayne Allard |
| Before Party: | Republican Party (United States) |
| After Election: | Mark Udall |
| After Party: | Democratic Party (United States) |
The 2008 United States Senate election in Colorado was held November 4, 2008. The primary elections were held August 12, 2008.[1] Incumbent Republican U.S. Senator Wayne Allard decided to retire instead of seeking a third term. Democratic nominee Mark Udall won the open seat, making this the first time a Democrat won this seat since 1972, and that Democrats held both Senate seats since 1979.
The election featured an open contest because incumbent U.S. Senator Wayne Allard declined to seek re-election. He honored his 1996 pledge to serve no more than two terms in the U.S. Senate and announced that he would retire from his service to the US Senate and not seek a 3rd term, leaving Colorado's Class II Senate seat open. Both parties believed this senate contest would be one of the most competitive senate races during the 2008 election.[2]
| Source | Ranking | As of | ||
|---|---|---|---|---|
| align=left | The Cook Political Report[3] | October 23, 2008 | ||
| align=left | CQ Politics[4] | October 31, 2008 | ||
| align=left | Rothenberg Political Report[5] | November 2, 2008 | ||
| align=left | Real Clear Politics[6] | October 28, 2008 |
| Poll source | Dates administered | Mark Udall (D) | Bob Schaffer (R) | |||
|---|---|---|---|---|---|---|
| align=left | Hill Research Consultants[7] | August 26–28, 2007 | 45% | 40% | ||
| align=left | Ciruli Associates[8] | September 12–15, 2007 | 36% | 35% | ||
| align=left | SurveyUSA[9] | October 27–30, 2007 | 48% | 41% | ||
| align=left | Rasmussen Reports[10] | November 28, 2007 | 41% | 42% | ||
| align=left | Research for Change[11] | December 3–5, 2007 | 39% | 37% | ||
| align=left | Rasmussen Reports[12] | February 11, 2008 | 43% | 44% | ||
| align=left | McLaughlin & Associates/ Coalition for a Democratic Workplace[13] | March 6–9, 2008 | 44% | 32% | ||
| align=left | Rasmussen Reports | March 17, 2008 | 46% | 43% | ||
| align=left | New Leadership USA/TargetPoint[14] | March 31 – April 7, 2008 | 45% | 45% | ||
| align=left | Rasmussen Reports[15] | April 16, 2008 | 45% | 42% | ||
| align=left | Rasmussen Reports | May 19, 2008 | 47% | 41% | ||
| align=left | Rasmussen Reports[16] | June 17, 2008 | 49% | 40% | ||
| align=left | Garin-Hart-Yang/DSCC[17] | June 15–17, 2008 | 46% | 37% | ||
| align=left | Quinnipiac[18] | June 26, 2008 | 48% | 38% | ||
| align=left | Public Policy Polling (PPP)[19] | July 10, 2008 | 47% | 38% | ||
| align=left | Keith Frederick[20] | July 22, 2008 | 48% | 39% | ||
| align=left | Rasmussen Reports | July 22, 2008 | 49% | 46% | ||
| align=left | Quinnipiac[21] | July 24, 2008 | 44% | 44% | ||
| align=left | Rasmussen Reports | August 13, 2008 | 50% | 42% | ||
| align=left | Hill Research Consultants[22] | August 24, 2008 | 41% | 38% | ||
| align=left | Tarrance Group[23] | September 3, 2008 | 41% | 40% | ||
| align=left | Public Policy Polling[24] | September 21, 2008 | 48% | 40% | ||
| align=left | Quinnipiac[25] | September 14–21, 2008 | 48% | 40% | ||
| align=left | Rasmussen Reports | September 23, 2008 | 46% | 44% | ||
| align=left | Denver Post[26] | September 29 – October 1, 2008 | 43% | 38% | ||
| align=left | Ciruli Associates[27] | October 1, 2008 | 45% | 38% | ||
| align=left | Rasmussen Reports | October 16, 2008 | 51% | 44% |