Former Sen. Ben Nighthorse Campbell announced today [2] he will not run for governor. He's also not endorsing any of the current candidates:

Campbell declined to endorse either of the two Republicans remaining in the race, Rep. Bob Beauprez and former University of Denver President Marc Holtzman. "I feel the best candidates haven't emerged yet," Campbell said.

It seems that our former Senator is disenchanted not only with politics, but with the right-wing of the Republican party.

You can't be held to a strict ideological code that you can't do anything about. What they want is absolute obedience." Campbell said. He refused to name names.