(The following article is taken from the U.S. Department of State publication USA Elections in Brief.)
Elections for the U.S. Congress can be as competitive and important as those for president. This is because of the central role that Congress plays in making laws.
Unlike a parliamentary system where the chief executive comes from the parliament, the American system, as noted, separates the legislature and the presidency. Presidents and legislators are elected separately. Although a sitting president may propose laws to Congress, they have to be drafted in Congress by his allies within that institution, and must be passed by the Congress before being sent back to the president for his signature. The House and Senate are legally and politically independent of the will of the president.
Within Congress, party discipline is less strictly observed in the American system than in parliamentary systems. It is fairly easy for members of Congress to vote on policies as they think best, including what they think best for winning their own reelection. As a result, congressional leaders must put together a winning coalition one member at a time, rather than count on automatic support from highly disciplined parties. This makes every congressional legislative victory difficult to obtain. Thus, Congressional elections are important to the nation, as Congress is powerful, and difficult to predict; and so are individual congressmen.
House and Senate Differences
The House and the Senate have nearly equal powers, but their means of election are quite different. The founders of the American Republic intended members of the House of Representatives to be close to the public, reflecting the public's wishes and ambitions. Therefore, the Founders designed the House to be relatively large in order to accommodate many members from small legislative districts, and to have frequent (two-year) elections. Originally, a two-year term was considered by some to be too long. In the days when transportation was by horse, a two-year term in Washington could keep a congressman away from his constituents for two years. Today, the concern is that elections every two years force congressmen to fly back to their districts every weekend or so to shore up political support.
Each House seat represents a unique geographic constituency, and, as noted above, every member is elected as sole representative from that district by plurality rule. Each of the 50 states is assured of at least one seat in the House, with the rest allocated to the states according to population. Alaska, for example, has a very small population and therefore holds only one seat in the House. California is the mostly highly populated state and holds 53 seats. Following each decennial census, the number of seats assigned to a state is recalculated to account for changes in state populations during the past 10 years, and state legislatures redesign congressional district boundaries within states to reflect changes in the number of seats assigned to the state or population shifts within the state.
The Senate was designed for its members to represent larger constituencies — the entire state — and to provide equal representation to that body of each state, regardless of population. Thus small states possess as much influence (two senators) as large states in the Senate.
Senators were originally selected by the state legislatures. It was not until enactment of the Seventeenth Amendment to the Constitution in 1913 that senators were directly elected by their state's voters. Every state has two senators elected for staggered six-year terms, with one-third of the Senate seats up for reelection every two years. A senator is chosen by plurality vote of the state electorate.
Loyalty to Party or Person
In the past, congressional elections tended to be "party centered," as many voters held long-term loyalties toward one political party or the other and tended to vote along party lines for Congress. The individual personalities and performances of office-holders may have only marginally added to or subtracted from voter support. In recent decades, the views and personalities of individual candidates have become more central to electoral politics and have somewhat diminished the importance of party loyalties.
Indeed, since the 1960s, national elections have become increasingly candidate-centered. The growth of the media and the Internet, the importance of aggressive campaign fundraising, constant opinion polls, and other aspects of modern campaigning have made the voter more aware of the candidate as an individual. As a result, voters tend to weigh individual candidate's strengths and weaknesses along with party loyalties in deciding whom to support. The establishment of broad-based public education in the early 20th century and of higher education after World War II has also made voters more confident of their own judgment; and less reliant on party cues with respect to ballot choices.
In this context of candidate-centered elections, incumbent members of Congress fare very well, with reelection rates well above 90 percent. This is partly due to often bland media coverage of Congress, and particularly coverage of individual members by local media in their states or congressional districts. With this generally favorable media exposure and daily involvement with public policy issues — and individuals and groups that seek to influence policy — incumbents also tend to raise far greater sums of money with which to campaign. For these reasons and more, incumbents who run for reelection are very likely to win, no matter which party they belong to.