Facebook relies on third-party fact-checking for the majority of ads run on its social network.
That third-party fact-checker scrutinizes "public, newsworthy Facebook posts, including ads, with articles, photos, or videos." There is one exception to this fact-checking effort: political advertising.
This is at the heart of Facebook's latest controversy: The company refuses to fact-check political ads.
During his speech at Georgetown University in mid-October, Mark Zuckerberg laid out a full-throated defense of Facebook's reason for not fact-checking political ads.
Nearly as soon as Facebook began clarifying and defending its policy of not fact-checking political ads, criticism began.
But Facebook isn't the only major social media company facing the difficult question of how to deal with political advertising.
If Facebook were to ban political ads, it would run into another issue — one that Twitter is almost certain to face: deciding what is and isn't "political" speech.