Post notices are banners that can be added by mods to the top of a question. There are only a short list of them available, the list is site-specific, and they require Stack Exchange employees to create new ones.
You may be familiar with seeing them on some posts saying "This post contains content that needs citations from reputable sources."
There have been some complaints that notable questions about political or religious footballs get downvotes and/or close votes because of political or religious biases of the average reader of the site. This is especially true during Hot Network Questions (HNQ) raids, where we tend to get a lot of programmers with little experience in skepticism popping in.
There are many legitimate reasons to downvote a question - including if you think it is actually a political attack masquerading as a question - but expressing bona fide doubt in a claim made by a politician that you like or loathe is not one of them.
That we write a paragraph that explicitly warns against downvoting based on political view points, with a link to a FAQ article expanding on what is good and bad reasons for voting.
That we ask Stack Exchange to add this is a post notice.
That mods add the post notice to questions on the main site where it considered that they may be up or downvoted based on political prejudices rather than whether it is a high-quality question.
The inspiration is the subreddit Am I the Asshole? where people ask for moral feedback on their actions. A "stickied comment" on each question (their equivalent to post notices) warns readers:
Don’t downvote assholes!
Do upvote interesting posts!
Do you think this will help? If so, what would you like to see in the post notice?