Unlike the DCCC did for their House Candidates in 2018 the DSCC has done a very poor job for 2020. They always relying too much IMO on recruiting former Governors or Senators.
Feingold, Bayh, Strickland = They all lost in 2016.
Now they're trying Hickenlooper who barely squeaked by his own Election in 2014. Triple LOL. He might win in 2020 but it won't be a blowout like everyone is predicting.
Most of the Pundits said Ron Johnson was a GONER in WI in 2016 and he wasn't.
Important to point out that Feingold, Bayh, and Strickland all lost in states where Trump was victorious. Granted, Johnson surprised the polls and pundits.
I don't think there's much "might-win" for Hickenlooper in Colorado. It's a state that has been rapidly sliding away from the GOP. And if he was still elected governor by ~3.5% during a red wave year, then I don't see what chance that Gardner has in 2020 unless it's a massive GOP blowout nationwide.
To answer the question, I'll go along with pretty much everybody else: Gardner and Jones.
