Heitcamp has a brother running a radio show at least 3 hours a day touting his sister or her platform so the name recognition is ways up there. Further, to hear Heidi, she sounds like a conservative Republican somewhere to the right of Goldwater.
Berg is a Rino supreme having voted with the Rats to raise the debt ceiling when he said he would not. His performance in the house has been un noticed and generally unremarkable.
That explains it.
Problem is.. once they get elected all that faux-conservative goes by the wayside and their guiding philosophy becomes "Democrat Party F3 (First..Foremost..Forever)!!"