Heidegger joined the NAZIs before they captured the state and very much wished to have his own philosophy elevated as something like the official NAZI ideology - resigned his position when it became obvious that the NAZI wasn't interested in his approach. An ideologue by some definition is someone who produces ideas with the aim of furthering a movement, state or similar force. By that definition Heidegger was a NAZI ideologue though perhaps "would-be NAZI ideologue" would be more accurate.