'I do not think," Nixon campaign aide Jeb Magruder told the Senate Watergate committee in the spring of 1973, "there was ever any discussion that there would not be a coverup." Mr. Magruder's lament aptly described the bureaucratic impulse to hide inconvenient facts that seizes every modern White House at some point. His testimony was brought to mind by the growing number of high-profile Republicans accusing the Obama White House of engaging in a coverup in the Benghazi case.

Much...