Humanities › Issues The U.S. Midterm Elections and Their Importance Share Flipboard Email Print JayDanny Cooper/Getty Images Issues The U. S. Government U.S. Political System History & Major Milestones U.S. Constitution & Bill of Rights U.S. Legal System Income Tax & The IRS Defense & Security Consumer Awareness Campaigns & Elections Business & Finance U.S. Foreign Policy U.S. Liberal Politics U.S. Conservative Politics Women's Issues Civil Liberties The Middle East Terrorism Race Relations Immigration Crime & Punishment Animal Rights Canadian Government View More By Robert Longley History and Government Expert B.S., Texas A&M University Robert Longley is a U.S. government and history expert with over 30 years of experience in municipal government and urban planning. our editorial process Facebook Facebook Robert Longley Updated November 06, 2019 The U.S. midterm elections give Americans the opportunity to rearrange the political makeup of the U.S. Congress in both the Senate and the House of Representatives every two years. Examples of Midterm Election Impact Falling right in the middle of the four-year term of the President of the United States, the midterm elections are often viewed as an opportunity to express satisfaction or frustration with the president's performance. In practice, it is not uncommon for the minority political party (the party not controlling the White House) to gain seats in Congress during the midterm election. In each midterm election, one-third of the 100 Senators (who serve six-year terms), and all 435 Members of the House of Representatives (who serve for two years) are up for reelection. Election of Representatives Since becoming federal law in 1911, the number of members in the U.S. House of Representatives has remained at 435. All 435 representatives are up for reelection in each mid-term congressional election. The number of representatives from each state is determined by the state's population as reported in the decennial U.S. Census. Through a process called "apportionment," each state is divided into a number of congressional districts. One representative is elected from each congressional district. While all registered voters in a state may vote for senators, only the registered voters residing in the congressional district that the candidate will represent may vote for representatives. As required by Article I, Section 2 of the Constitution, to be elected as a U.S. Representative a person must be at least 25 years of age when sworn in, have been a U.S. citizen for at least seven years, and must be a resident of the state from which he or she is elected. Election of Senators There is a total of 100 U.S. Senators, two representing each of the 50 states. In the midterm election, approximately one-third of the senators (who serve for six years) is up for reelection. Because their six-year terms are staggered, both senators from a given state are never up for reelection at the same time. Prior to 1913 and the ratification of the 17th Amendment, U.S. Senators were selected by their state legislatures, rather than by a direct vote of the people they would represent. The Founding Fathers felt that since the senators represented an entire state, they should be elected by a vote of the state legislature. Today, two senators are elected to represent each state and all registered voters in the state may vote for senators. Election winners are determined by the plurality rule. This means the candidate who gets the most votes wins the election. For example, in an election with three candidates, one candidate may receive only 38 percent of the vote, another 32 percent, and the third 30 percent. Although no candidate has received more than 50 percent of the votes, the candidate with 38 percent wins because he or she won the most, or a plurality of, votes. In order to run for the Senate, Article I, Section 3 of the Constitution requires that a person be at least 30 years old by the time he or she takes the oath of office, be a citizen of the United States for at least nine years, and be a resident of the state from which he or she is elected. In Federalist No. 62, James Madison justified these more stringent qualifications for senators by arguing that the "senatorial trust" called for a "greater extent of information and stability of character." About the Primary Elections In most states, primary elections are held to determine which congressional candidates will be on the final mid-term election ballot in November. If a party's candidate is unopposed, there may not be a primary election for that office. Third-party candidates are chosen by their party's rules, while independent candidates may nominate themselves. Independent candidates and those representing minor parties must meet various state requirements to be placed on the general election ballot. For example, they may be required to present a petition bearing the signatures of a certain number of registered voters.