Biden tops list of potential 2020 Democrats in new poll
Sanders overtakes Clinton in Colorado: poll
Sanders wins 49 percent support compared to Clinton's 43 percent in the poll.
Democrats will caucus in Colorado on March 1, when voters in a dozen states hold contests.
Colorado is seen as one of the best states for Sanders to pull out a victory.
A Quinnipiac University poll in November found Sanders trailing Clinton by 28 points, but that was before a tight finish to the Iowa caucuses and a Sanders victory in New Hampshire's primary.
In the new poll from the conservative Washington Free Beacon, he is seen as the more caring candidate by a 20-point margin.
Sanders also routs Clinton among youth voters, beating her by a 46-point margin among voters under 30, including a 40-point lead among women under 30.
Both candidates have been vying for the Hispanic vote in deadlocked Nevada, and Sanders narrowly edges Clinton with the group in Colorado, by a 41-38 margin. The Washington Free Beacon poll finds Clinton ahead among black voters by 12 points.
Respondents who supported Colorado's legalization of marijuana also flocked to Sanders, who has filed legislation in the Senate to decriminalize the drug.
Fifty-eight percent of Coloradoans who said legalizing marijuana was "very good" backed Sanders, while Clinton leads by a 44-32 margin among those who think the law has had a negative effect on the state.
The Free Beacon poll surveyed 1,144 potential Democratic caucus-goers from Feb. 16 to 17 and has a 2.98 percent margin of error.