Jack Dorsey says that Twitter will stop all political advertising.

We've made the decision to stop all political advertising on Twitter globally. We believe political message reach should be earned, not bought.

Jack specifies this policy includes both candidate and issue ads.

Best news from a social media company in a really long time. Unusual for a social media company, Twitter is putting the right thing to do ahead of profits. I wish other social media companies like Facebook would adopt the same policy.