“Swiftboating” is an untrue or unfair political attack or smear campaign. It’s similar in meaning to mudslinging.
The term comes from the 2004 presidential campaign when the Swift Boat Veterans for Truth produced a series of television ads and a bestselling book that challenged Kerry’s military record and criticized his subsequent antiwar activities. Kerry himself had served for four months as a swift boat commander in Vietnam.
The term “swiftboating” soon became used to describe political tactics of the group.