There is a section of every Facebook user profile that attempts to list them by political category.
In March 2018, amid story after damaging story about data-gathering and electoral manipulation using social media and increasing concerns over misuse of Facebook data for political purposes, a graphic that appeared online in March 2018 brought attention to how that information is tallied:
So apparently Facebook has you labeled as either Very liberal, liberal, moderate conservative or very conservative.
To view it you can go to settings > account settings > ads > your information > your categories > US Politics:
This tab does exist as part of the “Your Categories” subsection of users’ Ad Preferences tab, which includes the message, “Some of the ads you see are because advertisers are trying to reach people based on information they’ve provided on their profiles.” Clicking on the “Your Categories” tab shows users a separate note:
The categories in this section help advertisers reach people who are…