if this were a GOPer he’d be writing his resignation paper by now
Not exactly. The left-wing news media would be swarming his office in a feeding frenzy, however. Vitter didn't resign but there's no telling how this guy would have reacted, or how the polling in his home district would have gone. Vitter is from Louisiana and apparently they don't care down there.
“if this were a GOPer he’d be writing his resignation paper by now.”
I doubt that as there is no reason to resign.
GOPers have not resigned after sex scandals much mure salacious than this.