Conservatives are preparing to laud a potential Scott Brown victory in Massachusetts on Tuesday as a triumph of their ideology, but “to cite ideology rather than the economy in explaining the poll numbers is like analyzing the causes of Civil War without any reference to slavery or the rise of the New Deal without mention of the Great Depression,” E.J. Dionne writes in a sharp new column. Still, Obama has let the right define the battle. Both Dionne and Paul Krugman in The New York Times compare Obama to President Reagan. Even as Reagan’s numbers tanked, Dionne writes, he “was laying the groundwork for a critique of liberalism that held sway in American politics long after he left office.” Krugman writes that, when unemployment soared after Reagan’s 1981 tax cut, he had an easy answer: “Everything going wrong was the result of the failed policies of the past,” Krugman writes. “In effect, Reagan spent his first few years in office continuing to run against Jimmy Carter."