Protesters for Arn Menconi, a Green Party candidate for the U.S. Senate, rallied outside of the 9NEWS debate on Tuesday night.

Menconi did not reach the threshold -- 10 percent of the polls -- to participate in the only televised debate.

The protesters were heard during the broadcast, banging on the History of Colorado Center and yelling in support of Menconi.

Incumbent Sen. Michael Bennet (D-Colorado) were invited to debate on stage with Republican challenger Darryl Glenn, who currently serves as an El Paso County Commissioner.

Rewatch the debate here