You're right. We can't rule that out. I believe Chaffee (in the past) has indicated he might do a party switch.
I think it sucks. I also wish Steve Laffey had won the primary over Chaffee.
As it stands, the GOP will no longer have to worry about Chaffee soon. Most polls have him losing to the Democrat, Sheldon Whitehouse.
And that is with support from the RNC for him over his primary opponent.
But the RNC made a bet they couldn't win with a conservative there.
I wish Laffey had won too, but there just aren't enough Republicans up there. Of course, we can prevent a split by voting for every Republican we can, and I will, for everything except governor.