It's almost hard to imagine anything more undemocratic than the view that political officials should not debate American wars in public, but only express concerns 'privately with the administration.' That's just a small sliver of Johnson's radicalism: replacing Feingold in the Senate with Ron Johnson would be a civil liberties travesty analogous to the economic travesty from, say, replacing Bernie Sanders with Lloyd Blankfein.
If Feingold does it, if he wins this race in this year, it will not be as just another Democratic senator. It will not be as a maverick, nor even as an idealist. It will be as a signal that maybe, just maybe, people power can still beat the money power. That senators aren't just extensions of parties and presidents, and that politics can be about something more than Democratic toothpaste versus Republican toothpaste.