We argue that legislator shirking (voting on the basis of personal ideology rather than the interests of one's constituents) can exist, but its appearance should conform to the law of demand. We test and confirm this theory using votes on defense expenditure bills in the U.S. Senate in 1982. We assume the cost of shirking is relatively higher on narrowly focused bills on specific weapons systems with well‐defined beneficiaries, and relatively lower on general defense expenditure bills with uncertain final distribution of funds. We find greater influence for senators' ideology in general versus specific bill