Republican "-rat"

"Whatever the initial impulse or rationale, the term became controversial as far back as the 1950s. Sen. Joseph McCarthy (R-Wis.) famously used it to deride Democrats during his hearings investigating whether Communists had infiltrated the U.S. government. During the 1956 Republican convention, the usage was so common that it prompted the New York Times to report that dropping the '-ic' had become official party policy."

Maura Reynolds in the Los Angeles Times explores why Republican politicians insist on confusing nouns and adjectives.