Crouch, Nott, or Jugson, though I'd guess the latter more heavily -- Jugson's constantly in the center of the blood-purist aligned factions during one of the battle games, and mentioned as Dumbledore's example of a powerful Death Eater with a seat on the Wizengamot, as well.

Mr. White was selected for a particularly humiliating and harmful process, and coincidentally Quirrelmort had wanted to harm Lucius badly on the scale of framing him for attempted murder of his own son, and there's a pretty clear connection.