Actually, they do two kinds of vetting in advance: 1. How to spin the dirt that they’ve dug up so that nobody can mention, say, past crooked dealings by the candidate, without being branded for a “kook still pushing a conspiracy theory on an already debunked narrative”; and 2. How to completely destroy the candidate with “new, surprising revelations,” which they keep in reserve in case they don’t pan out. But they do not want squeaky clean model citizens. They want someone either dirty or incompetent, or preferably both, so that the deep state can own them and control them.