44. CLARENCE THOMAS (85 on the 2007 list) Clarence Thomas; most influential conservatives

Supreme Court Justice

Thomas has been on the Supreme Court for nearly two decades, making him one of the longest serving justices in history as well as a reliable conservative vote on virtually every issue.

If this sounds ridiculous, that's because it is: 36 of 111 Supreme Court justices served for over twenty years, including three currently on the court. If serving "almost two decades" makes you one of the longest serving justices, I am one of the greatest unicyclists in the world.