Democrats would be favored to keep all of the seats they currently have in that class. They would be more likely than not to pick up NC and ME (without Collins) with TX, AK, ME (with Collins) and possibly KS and MT constituting the next tier of pickup opportunities. Maybe IA and SC on a very good night.
NC and ME would be
very very high on that list of pickup opportunities... Susan Collins could finally be defeated with an overwhelming turnout from the state's Democrats - call her "Susan Collins-McConnell" in every single ad. Thom Tillis also doesn't strike me as a great gifted politician rather than someone that just got extremely lucky.
I'd argue that Alaska is the real upset possibility - more than Texas, Iowa, or SC. Alaska has the makings of a real competitive race if everybody that is not a right-winger in the state comes together and backs somebody very strong.