If they do stay home, then some good GOP house members(and there are a few) will be ousted. Oh well. I guess the US is going to become just like Massachusettes and New Jersey. Wonderful.
While I don't advocate staying home, myself -- I'll be voting for genuine conservatives down ticket, and either voting third party at the top or else leaving it blank altogether -- that's the inevitable risk the Republican party takes in running a RINO who, like a parrot suffering from Tourette Syndrome, reflexively and incessantly disses both said party's base and their conservative positions on the issues.
McCain can either meet the base at least halfway, on the specific issues on which they most profoundly disagree with him... or else accept the logical consequences of not doing so, like a mature, rational adult.