In a literal sense, no. Not any more than "rightists." You can say it's supposed to be like "right winger" but that brings up the question of how exactly you are personally using the term today to make your point, which, well, is clearly a bit arbitrary. Further, "right winger" would be one who takes the action of "right winging" which would simply mean "being on the right wing" but root words for leftist translate to "one who lefts" which would be one who takes left actions, as opposed to left-wing actions. That means that a true "leftist" would have to always take the furthest left action, rather than just taking any action that was more right than left over half the time.
Since neither side of the political spectrum quite represents any specific and coherent way of being, there can be no such thing as a "rightist" or a "leftist."
Still, people will speak however they wish.