I don’t know about OK runoff laws.
But Dahm isn’t a splitter. The first guy to announce against Langford was Jackson Lehmeyer, a local pastor. I don’t think he was going anywhere against Langford. But he got the backing of the head of the Republican party in OK because he wasn’t Langford.
Dahm is a more experienced candidate against Langford.
He understands that the staff in DC perpetuate the deep state and would bring a new set as Senator.