In the end this sort of speculation may over-estimate the extent to which midterm voters who are on the fence about participating really care about Brett Kavanaugh. Your average SCOTUS-obsessed “base” voter is far more likely than others to show up and pull the party lever no matter what happens in this or that confirmation fight. You don’t get extra votes for being excited or enraged, and you don’t lose partial votes for being discouraged or disappointed. A lot of registered voters skip midterms routinely. A lot of midterm voters are either locked into partisan positions that are nearly unshakable, or are simply reacting to their overall perceptions of the president, whose perceived job performance is the single most important variable.
So it may be at the margins, and in very close races, that the fate of Brett Kavanaugh, and who is held responsible for saving, abandoning or defeating him, matters on November 6. And there are all sorts of possible twists in how this works out. MAGA people may have been convinced by the president and his conservative media pack to ignore every danger sign that might normally draw them to the polls to defend their party’s hegemony–you know, since polls, negative media stories and the enthusiasm of the other party are all fake news phenomena. Perhaps an actual defeat over a Supreme Court nomination will shock them out of their complacency. But it’s not a possibility you’d want to put down as collateral on a loan.