The ghost of Ronald Reagan haunts the Republican presidential primary campaign. Consider that in the GOP debates, Reagan’s name has been uttered 72 times and by 16 of the 17 original candidates.

Reagan’s popularity among Republican presidential hopefuls is understandable. Reagan oversaw an economic recovery and contributed to ending the Cold War. More than anything, his sunny optimism helped many Americans believe that the United States could once again become, as Reagan (paraphrasing John Winthrop) put it, a shining city upon a hill. All of this helps explain why Reagan often ranks near the top of polls asking the public to name their favorite past president.