Is the recent increase in email spam due to Google's politician policy?

Google has instituted a policy of letting politicians through their spam filter.

My theory is that when I open these emails in my inbox, they load remote assets and the spammers see that I'm reading their emails and they send me more spam or resell my email address.

Is this possible or is it just the prevailing theories of spammers getting more clever about breaking through the spam filters and/or an increase in data breaches?