So there are the results of my survey:
509 responses
Bernie Sanders 25.1
Elizabeth Warren 16.1
Kirsten Gillibrand 5.3
Steve Bullock 4.1
Amy Klobuchar 3.9
Tammy Duckworth 3.8
Kamala Harris 3.3
John Hickenlooper 3.2
Maggie Hassan 1.2
Other 40.8
Was there an initial question to ask if they would vote in the Democratic primary, or was this poll question for everyone? If the latter, then I'd assume that "other" would be mostly Republicans.
My survey question was:
If you would like to see a Democrat win the 2020 presidential election, which of these candidates would you vote for?