Other forms: leftists
In politics, a leftist is someone who tends to support progressive or socialist ideas. Leftists generally favor bigger government and policies that result in economic and social equality.
This political term, in use since the late 19th century, is from left, a word that came to mean "the democratic or liberal party." This meaning goes back to the seating arrangement of legislators in the Estates General during the French Revolution: those seated on the left supported the revolution, and came to be called la gauche, or "the left." Leftists is just another way to describe anyone with progressive or liberal political beliefs.