That'd be Socialists.
Several bloggers have listed members of Congress by name under headlines like "Why do Americans Keep Electing These Socialist Politicians to Congress??" and "Socialist Party of America Releases The Names of 70 Democrat Members of Congress Who Are Members Of Their Congress."
The list -- actually a roster of Congressional Progressive Caucus members (mostly) from Wikipedia -- includes Florida Democrats Corrine Brown, Alcee Hastings and Frederica Wilson.
Huh? See how the bloggers' claim stacked up on the Truth-O-Meter. Hint: Lots of flames.