This chapter looks at the level of competition between the parties, the major theories as to what sustains two-party politics, and the efforts by minor parties and independent candidates to break the two-party pattern. Congress was a different story from 1932 to 1980, when Democrats controlled both houses most of the time. The partisan tilt of the safe seats in state legislatures has shifted during the past two decades, reflecting the partisan swings in congressional elections. After big Democratic gains in 2006 and 2008 state legislative contests, Democrats lost more than 900 state legislative seats during President Obama’s administration. Bruce Oppenheimer and others have suggested another alternative: New patterns of residential mobility can reduce party competition. As people have become more mobile, they are more able, and more inclined, to move to areas where like-minded people live. The most frequent explanation of the two-party system ties it to the nature of American electoral institutions.