What politicians can and can't say on Facebook

• They can't include profanity, as Trump's campaign found out.
• They can't embed social media posts that have been flagged by a fact checker.
• While not held to standards on factual matters, they have to follow Facebook's other community standards, such as those on hate speech.

What they can say:

• They can make just about any factual claim they want, including repeating verbatim a false claim that has already been labeled elsewhere as false. That means they can misstate their own record or that of an opponent.

Between the lines: Here's where it gets even messier. Politicians can take an already debunked claim and repeat it in their own ads. A regular user, meanwhile, can't take a false claim from a politician's ad and repeat the same words without violating Facebook's rules. They are, though, free to share that politician's ad.

The bottom line: Politicians still have a lot of room to mislead voters, especially when they can target different messages to different demographic groups.

Go deeper: Elizabeth Warren declares open season on Facebook's false ad policy