Julian E. Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter," published by Times Books, and editor of a book assessing former President George W. Bush's administration, published by Princeton University Press.

Next week voters in New York's 26th Congressional District will go to the ballot box to replace Rep. Christopher Lee, who resigned after a scandal involving a photo of himself shirtless that he sent to a woman he met online.

Like other special elections in the last two years, the rumble in the 26th has drawn the attention and resources of both national political parties. What would have ordinarily been a local race is seen as having big implications for 2012.

Until April, few Democrats thought this race was worth contesting. The 26th is one of the most conservative districts in New York, presumably a safe Republican seat. But then something happened. Rep. Paul Ryan of Wisconsin released his budget plan, which included a drastic overhaul of Medicare and Medicaid. Many of his GOP colleagues, fearing trouble on the campaign trail, distanced themselves from the plan as soon as the details were released.

In New York, Democrats pounced. The party has been able to generate substantial support for its candidate, Kathy Hochul, by connecting the dots between New York, Washington, and Wisconsin. Her ads have hammered away at her Republican opponent, Jane Corwin, for endorsing Ryan's proposal and supporting "a budget that essentially ends Medicare." She also supports, they add, reductions in Social Security benefits....