Sen. Michael Bennet (D-Colo.) leads his primary opponent by a healthy margin ahead of the August 10 matchup.

53 percent of Democratic primary voters said they would choose Bennet over his opponent, former state House Speaker Andrew Romanoff (D), who drew 36 percent of the vote.

Bennet's been seen as potentially vulnerable in the primary or the general election since having to been appointed to the seat, filling the spot left by Ken Salazar, who resigned as senator to become secretary of the Interior.

To that end, the White House has tried to clear the field for Bennet, having dispatched deputy chief of staff Jim Messina months ago to talk to Romanoff about federal positions for which Romanoff had applied.

In terms of a Republican challenger, Weld County District Attorney Ken Buck leads former Lt. Gov. Jane Norton (R), 53-37 percent.

Bennet fares less well against the potential Republicans than he does against Romanoff, though. Buck leads Bennet 46-43 percent in a hypothetical matchup, while Norton leads Bennet, 47-44 percent.

The poll, conducted by SurveyUSA, has a 2.6 percent margin of error.