Nevertheless, political analysts say, one rotten apple — or even the scores of them picked up in the past two decades — does not spoil the barrel. “I’ve studied American political corruption throughout the 19th and 20th centuries, and, if anything, corruption was much more common in much of those centuries than today,” said Larry J. Sabato, the director of the University of Virginia’s Center for Politics.

What has skyrocketed, he argues, is the public perception that politicians are corrupt. And to an extent, the numbers back him up.

The Justice Department’s public integrity section, which prosecutes official corruption at all levels of government, reports annually the number of public officials it has charged with corruption or convicted of corruption-related crimes. The data cover not only elected officials, but public servants from cabinet secretaries to enlisted soldiers.

Convictions of federal officials dropped nearly a quarter from 1989 to 2011, the most recent year for which figures are available. Convictions of state officials doubled, thanks in part to a sharp one-time increase in 2011. Local officials’ convictions have remained comparatively steady.