It's silly for Republicans to bet everything on Kavanaugh. So he gets confirmed, but then the House flips parties and the Democrats can investigate with all relevant witnesses subpoenaed. And their hearings are all public and so is their final report. They can investigate Trump's tax fraud as well. Everyone will know exactly what Kavanaugh (and Trump) did. Their reputations will be in tatters not because Democrats are out to smear them, but because of the bad things they actually did.
The optics for the Republican Party are lethal. Everyone will know they really are the party of rapists, fraudsters, racists, etc. Their diehard (rapist, fraudster, and racist) base may still support them but most people will recoil in horror.
And all this is so easily avoided: Just vet your candidates carefully before nominating or appointing them and reject the problematic ones. It's something every HR department in every successful company does every day. Apparently Trump is a lousy CEO.