That's two seats that should have been sure things for Republicans (SD and KS) flipped upside down in the matter of a month. Now republicans are going to have to pour money into races they never thought they'd have to fight for.
I'm not sure if the GOP will spend in South Dakota. They'll definitely start shifting money into Kansas (likely from Oregon, Michigan, and New Hampshire), but they might think that Rounds can squeak by the split field without any money. It won't take long to find out though, because the DSCC putting $1 million into the state on top of Mayday PAC's pro-Weiland ad buy has definitely upped the stakes.