The poll, which was conducted August 28 - September 1, showed widespread discontent with both political parties, with the Libertarian candidate garnering an unusually high 5% of the vote.
The poll also found a significant gender gap. Bennet led among women by 15 points, while Buck was leading by 9 points among men.
Buck made headlines during his campaign for the GOP nomination when he joked with voters at a rally that they should vote for him "because he does not wear high heels." Buck's opponent for the nomination, Jane Norton, used video of the comment to make Buck seem insensitive.
Buck has also said he opposes abortion even in the case of rape and incest.
Public Opinion Strategies and FM3 Research also found Bennet with stronger support among Democrats than Buck has among Republicans. This is consistent with recent polling from other companies that shows Democrats coalescing around Bennet after a divisive primary.
The poll showed independents generally backing Bennet, but warned that that could change given the large number of undecided voters.
The margin of error for the survey was 4.51%