Well, no. Not "politicians". No president has been indicted before- but plenty of mayors have been indicted and convicted. Plenty of governors too; something like 4 of the past 10 governors in Illinois have gone to prison. And vice presidents- VP Aaron Burr was indicted on two counts of murder while he was still in office. And then Nixon's VP was arrested and plead no contest to tax evasion, and then resigned to avoid prison time.