I get lots and lots of political email from lots and lots of entities associated with the two "major" parties and more than one "minor" party.
One thing I've noticed during the post-midterm period is that I get lots and lots of campaign email concerning the US Senate runoff in Georgia, and that pretty much all of that email is for incumbent Democrat Raphael Warnock, and almost none of it is for Republican challenger Herschel Walker.
Hmm ... when I go to my spam folder, there's a crap ton of Walker campaign email.
So chalk one up for the GOP claim against Gmail.
I think I know why.
The Democrats send me all kinds of email begging me for campaign contributions.
The Republicans do too.
But the Republicans also fill my inbox with email purporting to be of the "newsletter" variety, to which I have not intentionally subscribed. Many iterations of this email type consist of nearly exact copies of other iterations. "Patriot Brief." "Patriot United News." "Conservative Intel." Etc. Some of these have more disguised titles and look almost like the more conventional "crazy headline of the day" newsletter format.
I like getting campaign email because it keeps me up on the latest strategies and approaches whether I support the candidates or not.
I hate getting "newsletters" that I didn't ask for.
When I get a "newsletter" I didn't ask for, I tell Gmail to unsubscribe me from it and send it to spam.
I suspect that many other people feel, and do, likewise.
And I suspect that Republicans run a lot of campaign email and a lot of these "newsletters" through the same handful of email servers / IP addresses, causing their campaign email to to get caught in the same (user-generated, or at least based on revealed user preference) spam traps the "newsletters" get sent to.
That's my theory, anyway.