Sean O'Hanlon scored the only goal to keep MK Dons on course for a play-off place and push his former club Swindon ever closer to League Two.
Centre-half O'Hanlon rose highest to nod home Peter Leven's 16th-minute corner to leave Swindon without a home win in their last 12 games.
On-loan Robins striker Calvin Andrew rattled the crossbar in first-half stoppage time.
Mat Doumbe and O'Hanlon had chances to extend the Dons' lead in the second half before a miserable afternoon for Paul Hart's side was complete with defender Andy Frampton was dismissed 10 minutes from time for a second bookable offence.
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