Democrats controlled the chamber from 1973 until the 2010 elections. The second year of the biennium has a flexible start date and is usually shorter than the first year. !function(){"use strict";window.addEventListener("message",(function(e){if(void 0!==e.data["datawrapper-height"]){var t=document.querySelectorAll("iframe");for(var a in e.data["datawrapper-height"])for(var r=0;r