Don't get where the idea that McGrath is the electability candidate came from, besides the fact that she's a moderate white lady (ok that's probably it). She lost the 2nd most democratic district in Kentucky in a blue wave year.
I don’t think she’s really electable for the reason you say but I still think Booker is even less so. This one poll, pretty inconsistent with everything else we’ve seen so far by the way, doesn’t change that. I just find it hard to believe that a black left progressive who supports the Green New Deal has a snowball’s chance in hell in Kentucky. Even if he does have a relative advantage over McGrath right now, he definitely won’t after he’s run through the McConnell machine.