The poll, which had a 4% margin for error, has Ken Buck leading Michael Bennet 46-41 with 7% undecided.
The poll shows Republicans have been quicker to coalesce around Buck's candidacy than Democrats have been to unite around Bennet. Both candidates are coming off heated primary races.
Rasmussen has primarily worked for Republican clients, and has been accused in the past of over-estimating Republican representation in their models.
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