Anecdotally, I used to receive texts and emails from both main US parties, and the differences are stark. From my experience, Democrat pamphlets usually focus

Anecdotally, I used to receive texts and emails from both main US parties, and the differences are stark. From my experience, Democrat pamphlets usually focus on public policy improvements, e.g. healthcare, transportation, or economy, whereas Republican ones read more like a list of complaints or more politically charged issues, on e.g. border protection and immigration, religion, moral values. The latter also have a bigger chance of being more hyperbolic. So I guess that, at least in my case, a spam filter configured around my preferences would be more likely to discard content regarding Christianity, traditional family values, stuff like that, and I would expect users in academia, likely on the liberal side of the political spectrum, to observe a similar effect.