Democrats. Republicans will inevitably piss away 2-3 races they should otherwise win. Again.
Is that true objective thinking or a bias speaking when there is no evidence a candidate in this field would do that?
Not that Iowa was ever in the Republican camp, but Ernst likely fits the bill of the O'Donnell type who blows a potentially winnable race. Tillis is another subpar candidate who may piss away a winnable race.
Overall, though, I think you're right in that Republicans are finally cutting down on these situations.