According to research by political scientists and economists, voters actually put more weight on what they think is in the country's best interest than their own self-interest. Researchers have been unable to find much of a link between individuals' self-interest and their position on a range of public opinion questions, or on their voting behavior. For example, higher-income people, who stood to benefit much more from the second Bush tax cut than lower-income people, expressed only slightly stronger support for it. And those old enough to receive Medicare were slightly less in favor of expanding it to cover drug insurance than everyone else was.
Source: Alan B. Krueger, "A Study Looks at What the Public Knows, Or Doesn't Know, About Economics and Why," The New York Times, Thursday, April 1, 2004, Late Edition - Final, Section C, Column 1, Business/Financial Desk, Pg. 2, Economic Scene. Article refers to report by Alan S. Blinder and Alan B. Krueger called, "What Does the Public Know About Economic Policy, and How Does It Know It?" (Alan B. Krueger is a professor of economics and public affairs at Princeton University, firstname.lastname@example.org).