That Mr. Bush won by a relatively narrow margin matters little in a historical context, Professor Cain and others said. Lincoln, who oversaw the most radical political break in American history, was elected with just 39.8 percent of the popular vote in 1860.
Yet David R. Mayhew, a professor of political science at Yale, cautioned against reading too much into any of the numbers. Mr. Bush’s victory could be seen as extraordinary - the first time a president won re-election after failing to win the popular vote in his first term - or as commonplace, since two-thirds of presidents who have sought re-election have won.
“I think this is mostly an ebb-and-flow election,” Professor Mayhew said.
Professor Wilentz of Princeton said that even if the 2004 victory was an incremental one, that should not comfort the Democrats. He said Mr. Rove and Mr. Bush now have a chance to do what Hanna and McKinley never did: Lay the foundation for lasting Republican dominance.
“The Republicans are basically unchecked,” Professor Wilentz said. “There is no check in the federal government and no check in the world. They have an unfettered playing field.”
Until the next act of God, that is.
