https://www.reuters.com/article/us-usa-election-facebook/warren-campaign-challenges-facebook-ad-policy-with-false-zuckerberg-ad-idUSKBN1WR0NU >U.S. Senator Elizabeth Warren's Democratic presidential campaign this week challenged Facebook's policy that exempts politicians' ads from fact-checking, by running ads on the social media platform containing the false claim that Facebook CEO Mark Zuckerberg endorsed President Donald Trump's re-election bid.