Before revision:  We compare ads run by candidates, parties, and two types of outside groups: those that disclose their donors and those that are funded by dark money . Dark money outside groups ran ads with the most negative sentiment on average, whereas candidates ran ads with the most positive sentiment .
After revision:  We compare ads run by candidates, parties, and outside groups, which we classify by (i) their donor transparency (dark money or disclosed) and (ii) the group's permanence (disappearing after 2018 or re-registering). Ads run by dark money . Dark money outside groups ran ads with the most negative sentiment on average, whereas candidates ran ads with the most positive sentiment .