Hmm. He didn't want to face a tough, drawn out Democratic gubernatorial primary. However, the last time Colorado GOP won the governorship was in 2002. It's long time for the GOP to pick up the governorship.
I have CO-GOV as Tossup.
Honestly, putting my inner partisan hack aside and just looking at current trends, the expected environment and Colorado's gubernatorial history, a toss-up seems like a stretch. Since 1976, there has only been one Republican Governor, and that was Owens, who I might add barely won his first term
(even as he crushed it the 2nd time around). Gubernatorial elections have not been kind to Republicans, and that was true even before Colorado started trending Democratic in earnest. Now the COGOP has to cope with overall unfavorable state trends, probably a decent Democratic candidate that can self-fund bigly, and most of all, a highly unfavorable national environment where despite all else, Trump is likely to be pretty unpopular in Colorado.
Personally I'm starting out at Leans D until something convinces me otherwise.