The poll, which was conducted August 20-22 and has a margin of error of 4.6%, shows Buck receiving 49% of the vote to Bennet's 40%.
Ipsos showed Bennet leading Buck 27%-17% among independents, but capturing just 79% of Democrats. Buck was supported by 86% of Republicans.
The Ipsos/Reuters poll also showed GOP gubernatorial nominee Dan Maes doubling the support of third-party challenger Tom Tancredo, 33%-16%. The poll found that, without Tancredo in the race, Hickenlooper and Maes were tied at 45%.
This also differs from recent polling that has shown Hickenlooper with a lead regardless of whether Tom Tancredo remains in the race.
Maes won the Republican nomination earlier this month after a scandal-plagued primary season for the GOP. Prior to Maes's primary victory, Tancredo entered the race as a member of the American Constitution Party.