John Sides digs up a 2009 study measuring the damage done by various -gates. The researchers "presented respondents with one of four vignettes about a hypothetical politician [named Mark Jones] enmeshed in a scandal":
The vignettes all had a negative effect on views of Jones, as you might suspect. But there are some interesting nuances. First, the financial scandal tended to matter more than the moral scandal. Second, the financial scandal’s impact was augmented by the abuse of power, but the abuse of power had less impact in the moral scandal. Third, the moral scandal had more impact on evaluations of Jones as a person than on evaluations of his job performance.
The Dish 