To test whether interest group politics do harm to a representative democracy, this paper simulates congressional district-level constituency opinion on abortion. Analyzing the relationship between the constituency opinion and NARAL's contributions in the 102nd and 103rd Congresses, this paper presents empirical evidence that NARAL's contribution decision is influenced by constituency opinion. The evidence, however, is mixed. Constituency opinion influences NARAL's decision on who will get its money. Constituency opinion, however, does not influence NARAL's decision on who will get more money. According to these results, financial representation by interest groups does not seriously cause harm to a representative democracy, but it can still bias the representativeness to some extent. An interest group may select legislators whose districts support its position less strongly and contribute a greater amount of money to the legislators.