I don't think the James O'Keefe stuff is as potent for McCaskill because she's already running as a raging liberal (at least comparatively by MO standards), but Bredesen was running as a really a center to center-right looking candidate. Shock impact is 0, maybe turns a couple votes away, but unlike the Bredesen thing, this is not blowing any cover or anything, Claire is not running on an inauthentic belief system, and everyone knows that.
Despite this, I still expect Hawley to win, albeit not from this, but I think the Kavanaugh vote has given him the edge. I had it at pure tossup before the vote, and kept shifting it from tilt R and tilt D, and actually was about to switch it back to tilt D because I was looking up her name and seeing good results for her from critical KC areas at the time, but then the next article I clicked on had her as a no on Kavanaugh. Since then, I have her race at lean R, Hawley 50-47.
The 'bombshell video' tells us what is already public record, she voted for a high capacity ban and has supported a bump stock ban (is that even bad in MO?). I love how the O'Keefe people make a big deal what some low level staffer thinks about policies. I'd love for a Dem to go undercover on some R Senate campaign and see the crazy stuff their staffers think.