Levitt's 1994 paper on campaign spending employs a unique identification strategy to control for the quality of each candidate (which in previous work had led to an overstatement of the true effect). It concludes that campaign spending has a very small impact on election outcomes, regardless of who does the spending. On the subject of federal spending and elections, previous empirical studies were not able to establish that members of Congress are rewarded by the electorate for bringing federal dollars to their district because of omitted variables bias. Levitt and Snyder (1997) employ an instrument which circumvents this problem and finds evidence that federal spending benefits congressional incumbents; they find that an additional $100 per capita spending is worth as much as 2 percent of the popular vote.