Mr. Reagan’s approval ratings rose sharply after he left office — from 53 percent in 1988, at the end of his time in office, to 73 percent by 2002, according to Gallup. But it’s not clear the Reagan election model can work in the 21st century, as America’s population has become more diverse. In 1980, Mr. Reagan thrashed Jimmy Carter by winning 55 percent of the white vote. Mr. McCain, as it happens, matched that percentage in 2008, but lost decisively to Mr. Obama. The difference, according to exit polls, is that whites represented 74 percent of the overall electorate last year, down from 88 percent in 1980. At the same time, blacks and Hispanics collectively accounted for 22 percent of the vote in 2008, up from 12 percent in 1980.

But demographics tell only part of the story. There is also the arrival of a new slate of pressing issues. It has been 20 years since Mr. Reagan’s plea to “tear down that wall” was answered by the fall of Communism. The 70 percent top income tax rate Mr. Reagan called confiscatory now stands at half that level. And the cultural appeals he made to blue-collar voters and evangelicals have lost their immediacy, displaced by economic concerns. Many remember that Mr. Reagan identified government as “the problem.” But today an increasing number of voters look to the government for security and stability.