The scenario for the democrats is difficult, but they have no real choices. The red-state Senators can oppose the nomination, which is probably a done deal anyway. But if they vote NO, they commit political suicide, and the Senate goes to 57-43. That is such a large margin that Trump can nominate my cat to the Federal bench and get 51 R votes. So the dems lose bigly.
The other option is, since this is a done deal, give the red-state democrats some “bipartisan” cover in the hopes it keeps them in office and keeps the Senate close to fight again another day. But they give up a moderate seat for a conservative on the Court for another generation. Yeah, that’s hard for them to swallow. But they really don’t have another viable option, because Kavanaugh is a done deal anyway.
This is all about what the Senate will look like in 2019, not whether Kavanaugh is confirmed.
Even voting for Kavanaugh may NOT be enough for the Dems in states where Trump won and won BIG, may NOT give them "cover", though, in the up coming election.