There are two basic types of elections — primary and general. In addition to the primaries and general elections held in even-numbered years, which include political races for the U.S. Congress, some states and local jurisdictions also hold “off-year” elections (both primary and general) in odd-numbered years for their elected officials.

A primary election is a nominating election in which the field of candidates that will run in the general election is chosen. Victory in a primary usually results in a candidate being nominated or endorsed by a political party for the general election.

A general election is an election held to choose among candidates nominated in a primary (or by convention, caucus or petition) for federal, state and/or local office. The purpose of a general election is to make a final choice among the various candidates who have been nominated by parties or who are running as independents (not affiliated with a major political party) or, in some cases, write-in candidates. Measures such as proposed legislation (referendums), bond issues (approving the borrowing of money for public projects) and other mandates on government also can be placed on the ballot.

In addition, many states provide for special elections, which can be called at any time, to serve a specific purpose, such as filling an unexpected vacancy in an elected office.

The elections in which Americans vote for their congressional representatives but not for their president are known as midterm elections. Every two years, Americans elect members of the U.S. House of Representatives to two-year terms and about one-third of their U.S. senators, who serve six-year terms. Voters also will select officials to state and local government posts.

Conventions are meetings sponsored by political parties for members of the party to discuss issues, candidates and campaign strategies. These meetings can last several days.

In presidential elections, after state primaries are concluded, each party holds a national convention to formally select the presidential nominee — usually the candidate who secured the support of the most convention delegates, based on victories in primary elections. Typically, the presidential nominee then chooses a running mate to be the party’s candidate for vice president.

Political parties hold national conventions only in presidential election years. The parties usually hold smaller, state-level conventions in other years. The Democratic National Convention will be in Charlotte, North Carolina, September 3–6, 2012. The Republican National Convention will be in Tampa, Florida, August 27–30, 2012.

A caucus is a meeting at the local level in which registered members of a political party in a city, town or county gather to express support for a candidate. For statewide or national offices, those recommendations are combined to determine the state party nominee. Caucuses, unlike conventions, involve many separate meetings held simultaneously at multiple locations. Both the Democratic and Republican parties have their own rules governing caucuses. Those rules vary from state to state.

American citizens ages 18 and older can register to vote. To register, voters must meet the residency requirements of their states, which vary, and comply with voter-registration deadlines.

Each federal elected office has different requirements, which are laid out in Articles I and II of the U.S. Constitution.

A candidate for president of the United States must be a natural-born citizen of the United States, be at least 35 years old and have been a resident of the United States for at least 14 years.

A vice president must meet the same qualifications. Under the 12th Amendment to the Constitution, the vice president cannot be from the same state as the president.

U.S. House of Representatives candidates must be at least 25 years old, have been U.S. citizens for seven years and be legal residents of the state in which they seek election.

U.S. Senate candidates must be at least 30 years old, have been a U.S. citizen for nine years, and be legal residents of the state in which they seek election.

Officials seeking state or local office must meet the requirements established by those jurisdictions.

They are held on the first Tuesday after the first Monday of November.

For much of U.S. history, America was a predominantly agrarian society. Lawmakers considered their convenience when choosing a November date for elections — after harvest time but before winter weather made travel difficult — as the easiest month for farmers and rural workers to go to the polls.

Because many rural residents lived a significant distance from the polls, Tuesday, rather than Monday, was selected to allow those who attended Sunday church services to begin travel after worship and still reach their destinations in time to cast their votes.

Lawmakers wanted to prevent Election Day from falling on the first of November for two reasons. First, November 1 is All Saints Day, a day on which Roman Catholics are obligated to attend Mass. Also, merchants typically balanced the accounts from the preceding month on the first of each month.

State and local governments determine the dates on which primary elections or caucuses are held. These dates, and the amount of time between a primary and general election, significantly influence how early candidates begin campaigning and the choices they make about how and when campaign funds are spent.

In the run-up to presidential elections, victories in primaries held very early in the election year, such as that in New Hampshire, can influence the outcome of later state primaries.

The Electoral College is the group of citizens designated by the states to cast votes for the president and vice president on behalf of state citizens. The process for selecting electors varies from state to state, but usually the political parties nominate electors at state party conventions or by a vote of the party’s central committee. The voters in each state, by casting votes for president and vice president, choose the electors on the day of the general election. The Electoral College, not the popular vote, elects the president, but the two votes are tied closely.

The Electoral College system gives each state the same number of electoral votes as it has members of Congress. The District of Columbia is allocated three electoral votes. There are a total of 538 votes in the Electoral College; a candidate for president must get 270 to win (a simple majority). All but two states have a winner-take-all system, in which the candidate who gets the most popular votes in the state is allocated all of the state’s electoral votes.

The electors usually gather in their state capitals in December to cast their votes. The electoral votes then are sent to Washington, where they are counted in the presence of a joint session of Congress in January.

If no presidential candidate wins a majority of electoral votes, the 12th Amendment to the Constitution provides for the presidential election to be decided by the House of Representatives. In such situations, the House selects the president by majority vote, choosing from the three candidates who received the greatest number of electoral votes. Each state would cast one vote.

If no vice presidential candidate wins a majority of electoral votes, the Senate selects the vice president by majority vote, with each senator choosing from the two candidates who received the greatest number of electoral votes.

The Electoral College is used only to select the president and vice president.

There have been 17 presidential elections in which the winner did not receive a majority of the popular vote cast. The first of these was John Quincy Adams in the election of 1824, and the most recent was George W. Bush in 2000.

The founders of the United States devised the Electoral College system as part of their plan to share power between the states and the national government. Under the federal system adopted in the U.S. Constitution, the nationwide popular vote has no legal significance. As a result, it is possible that the electoral votes awarded on the basis of state elections could produce a different result than the nationwide popular vote. Nevertheless, the individual citizen’s vote is important to the outcome of each election.

Several factors seem to influence voter turnout, which was approximately 41 percent of eligible voters in 2006 and 61 percent in 2004. Many observers believe that current registration laws hinder voter turnout. The demographic composition of the electorate, long periods of political or economic stability, predictable outcomes in many races and some candidates’ lack of popular appeal are other factors affecting voter turnout. Turnout tends to be higher in general elections than in primary elections. Turnout also tends to be higher in years in which the president is elected than in midterm elections.

The elephant represents the Republican Party, and the donkey represents the Democratic Party. Political cartoonist Thomas Nast created both images for the publication Harper’s Weekly in 1874. Nast created a marauding elephant to represent the “Republican vote.” Republicans quickly embraced the symbol as their party’s own.

In a separate cartoon, Nast criticized the Democrats for posthumously maligning a Republican by picturing the Democratic Party as a donkey or mule (animals considered stubborn and stupid) kicking a lion (the dead Republican). The Democratic Party, demonstrating a sense of humor, accepted the animal as its symbol, observing that it has many fine qualities, such as not giving up easily.

Voting in U.S. elections is conducted by secret ballot, and a voter’s choice is private. The “endorsement” of a candidate by an organization means the organization publicly supports the candidate and approves the candidate’s stand on issues. Although organizations can encourage members to join in that support, it is unlawful for them to coerce a member to vote against his or her own judgment.