I think that we either treat each coin equally or this whole concept falls apart. Every coin is potentially originating from criminal activity.
For me, campaign payment coins are clearly tainted.
It's a bit more complicated than that: when I receive cash euros, I don't have to worry about how they were previously used. But if you know the money comes from something illegal, you shouldn't get involved.
Maybe it's a bit like "aiding and abetting": it's totally fine to help someone, unless you know he's involved in a crime.