Bennet said he voted against the bill because it didn't do enough to reduce the debt.
"Washington once again has lived up to its reputation as the ‘Land of Flickering Lights.’ For four years in my town-hall meetings across the state Coloradans have told me they want a plan that materially reduces the deficit. This proposal does not meet that standard and does not put in place a real process to reduce the debt down the road," he said in a statement.
"While I do support many of the items in this proposal — for example, extending unemployment insurance, the wind production tax credit and tax cuts for most Americans — I believe they should have come in the context of a comprehensive deficit-reduction package. Without a serious mechanism to reduce the debt, I cannot support this bill."
Bennet is one of the bipartisan Gang of Eight senators who were working together earlier last year on a grand bargain to reduce the deficit.
His new job as chief fundraiser and recruiter for the Democrats' campaign committee could be an impediment to joining such bipartisan efforts in the future, and Bennet had expressed concerns that taking the job would hinder his work across the aisle.
Votes like these, in which he breaks with party ranks, might give him enough credibility to continue that bipartisan work despite his politicized position as head of the campaign committee.