Eight candidates were invited Tuesday to participate in the first televised debate in Colorado’s 2016 GOP primary race for U.S. Senate.

Colorado Republicans are working to pick a candidate to run against incumbent Sen. Michael Bennet (D-Colorado.)

Those invited to participate are:

  • Robert Blaha
  • Ryan Frazier
  • Darryl Glenn
  • Jack Graham
  • Jon Keyser
  • Peg Littleton
  • Jerry Natividad
  • Tim Neville

The 9NEWS/Lincoln Club of Colorado debate will take place at 7 p.m. on Tuesday, April 5. It will be broadcast, commercial-free, for one hour on Channel 20 and streamed on 9NEWS.com.

A second debate -- scheduled for Tuesday, June 7 -- will be open for all candidates who qualify for the primary ballot.

The Lincoln Club provided logistical support in reaching out to campaigns and 9NEWS will be solely responsible for the debate production, format, and questioning.

The invited campaigns were all unanimously deemed to be viable by a panel of political experts who reviewed material submitted by campaigns. The panel was assembled to determine which candidates would be invited due to a lack of polling or fundraising data this early in the race. Panelists were asked to make their decision based solely on who had a viable chance of appearing on the June primary ballot.

The lineup for the debate is not yet final. Campaigns who were not invited have been given a deadline of March 31 to provide any additional evidence of viability for the panel to consider.

The panel unanimously decided that the campaigns of Charlie Ehler, Jerry Eller, Michael Kinlaw, and Donald Rosier did not demonstrate a viable path to accessing the June primary ballot.

Ehler and Rosier did not provide materials for the panel to review by the Monday deadline.

Greg Lopez, who had announced a run, told 9NEWS he’s dropped out and is endorsing Natividad in the race.

9NEWS and the Lincoln Club were each represented on the panel that reviewed campaigns for viability, along with Floyd Ciruli (a pollster and political analyst for 9NEWS,) Peter Hansen (a political science professor and expert on the U.S. Senate,) and Kelly Maher (a Republican political operative and political commentator for 9NEWS.)

Several better-known Republicans have passed up the opportunity to run for U.S. Senate. Those remaining in the field are hoping to drum up support and name recognition.

Candidates have two paths to gain access to the June 28 GOP primary ballot. They can either win at least 30 percent support at the state party convention on April 9 or gather thousands of petition signatures from across Colorado and submit them to the Secretary of State for review.