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 two types of outside groups: those that disclose their donors and those that are funded by dark money and disappearing outside groups were more negative than transparent and re-registering groups, respectively .