Thanks to Libby Mitchell campaign manager Marc Malon and Pat McGowan campaign manager Brandon Maheu, who both photographed their own collections, I now have a good visual record of more than two decades of Joe Brennan campaign paraphernalia. Click the image below to enlarge.
Here's Richardson's logo (his buttons are similar, with the first and last name stacked above a shorter swoosh). There's definitely some similarity with certain Brennan designs.
Other campaigns should take note; Maheu and Malon have obviously been studying how to win Democratic primaries.