From the few polls I’ve read about this race, Steelman had the largest lead in a hypothetical matchup with McCaskill - something on the order of 10-12 points. I confess I don’t know much about Brunner or the other GOP primary candidates, but Steelman sounds like a very strong candidate for the general election.
I checked Realclear and she and Brunner were about equal. The race has closed but McCaskill is underwater as is Obama in MO. MO has shifted to the right since 2008 when McCain barely won. I worry about Brunner’s money. He’s been doing a Dewhurst dumping on Steelman to drive her down.