Each state chooses as many electors as it has representatives and senators representing it in Congress. Under the 23rd Amendment, the District of Columbia may choose no more electors than the state with the lowest number of electoral votes (in effect, three electors), although since that amendment's ratification the District's population has never reached the threshold that would otherwise entitle it to choose four or more electors. U.S. senators, representatives and federal government officials are barred from becoming electors; in practice, the two major federal parties frequently select senior state party and government officials (up to and including governors) to serve as electors.