Ideological polarization The effect on public opinion when many citizens move away from moderate positions and toward either end of the political spectrum, identifying themselves as either liberals or conservatives. The term can also be applied to the political parties. The opposite of ideological polarization is ideological convergence.

Ideology A relatively consistent set of beliefs and attitudes that seek to understand the political world and, in doing so, prescribe a means by which one might establish a better way of doing things. The two main ideologies within the United States are conservatism and liberalism. Ideological polarization has been a notable feature of American politics since the 1970s, but once a party gains power they usually attempt to govern in a pragmatic manner. There is often a very sharp difference between campaign rhetoric and the reality of government.

Impeachment In a literal sense, to make a formal accusation against someone. The House initiates impeachment proceedings but the Senate takes on the more important role. If that person is found guilty during an impeachment trial in the Senate they can be removed from office based on a two-thirds majority. The House only has to record a simple majority. Two US Presidents have been impeached; Andrew Jackson and Bill Clinton. Both however were acquitted at trial. Federal officials have been removed from office, but no Supreme Court justice has ever been impeached.

Imperial presidency A thesis derived from Arthur Schlesinger (1973) which emphasizes the strength of the US President. The use of the term ‘imperial’ is deliberate in that it evokes deep-seated concerns within the American mindset concerning the abuse of power. The alternative argument is called the imperiled presidency. Schlesinger put forward the imperial thesis out of concern that the presidency had exceeded its constitutional powers, and that President Nixon was out of control. A presidency is said to be imperial when it uses powers beyond those delineated by the Constitution. It should be noted that Schlesinger’s thesis very much captured the zeitgeist of the time. However, his motivations may have been in part shaped by his own political beliefs. Schlesinger had been an advisor to JFK (Hersh, 1998) and most liberals at the time loathed Richard Nixon. Whatever the motivation, the imperial presidency thesis remains the template for any assessment of presidential power.

Implied powers Those powers supported by the Constitution that are not expressly stated in it. Implied powers deviate from the original intentions of the founding fathers, who believed that Congress rather than the presidency should be the predominate body. One example of implied powers is the use of judicial review by the Supreme Court.

Income support Government programs that provide support to low-income Americans (such as welfare, food stamps, unemployment compensation and the Earned Income Tax Credit). The left-wing economist Thomas Piketty once claimed that the United States chose not to develop a European-style welfare state because they did not wish to subside a black underclass.

Incumbency effect Where the candidate already in office holds a considerable advantage over his/her opponent. Re-election rates are high, and a genuine contest often requires the resignation (or removal from office) of a popular incumbent. In many cases, incumbents usually face a stronger challenge during that party’s primary. There are many reasons for the high rate of incumbency including gerrymandering, their ability to raise pork for their constituents, name recognition and greater levels of campaign finance. Incumbents also have some perks of office.

Incumbency safety The relative infrequency with which incumbents are beaten in a general election. In some instances, a House seat is not even contested due to the existence of a popular incumbent.

Incumbent A politician running for re-election to the office he/she currently holds.

Independent agencies Government offices or organizations that provide government services and are not part of an executive department.

Informational theory The idea that having committees in Congress made up of experts on specific policy areas helps to ensure well-informed policy decisions. The main center of power in Congress rests with the committees.

Initiative A direct vote by citizens on a policy change proposed by fellow citizens or organized groups outside government. Getting a question on the ballot typically requires collecting a number of signatures from registered voters in support of the proposal. National plebiscites are not allowed under the Constitution.

Insider strategies Tactics used by interest groups within K Street to achieve their policy goals.

Interest group An organizations of people who share common political interests and aim to influence public policy by electioneering and lobbying.

Interest group entrepreneurs The prominent members of an interest group who define the group’s mission and its goals and create a plan to achieve them.

Intergovernmental organizations A term used to describe groups such as the National Conference of State Legislators and the National Governors Association (NGA) who represent decision-makers in the states. They are sometimes thought of as a glorified pressure group because they make their views known to members of Congress in the hope of persuading those in power. The profile of the NGA has grown in recent times.

Intermediate scrutiny standard The middle level of scrutiny the courts use when determining whether unequal treatment is justified by the effect of a law. The intermediate scrutiny standard is the standard used for gender-based discrimination cases and those cases based on sexual orientation.

Internationalism The idea that the United States should be involved in the affairs of other nations. This is usually based upon a mix of self-interest and moral obligation. Obama has said that America can no longer afford to act as the world’s policeman.

Investigative journalists Reporters who dig deeply into a particular topic of public concern, often targeting government failures and inefficiencies. Perhaps the most famous investigative 'journos' are Woodward and Bernstein during their uncovering of the Watergate scandal.

Invisible primary The period between candidates declaring their intention to run and the first contest of the primary season. The invisible primary enables a candidate to gain name recognition, money and an effective level of organization.

Iowa straw poll A fund-raising dinner during which any would-be Republican candidate for the White House is given the opportunity to make a speech. This is a visible aspect of the invisible primary.

Iron triangle A term used to describe the strong and secretive relationship between pressure groups, congressional committees (although they rarely take the decision) and government agencies in any given policy area for the mutual benefit of each party. The iron triangle reflects the undemocratic influence of pressure groups upon the political process.

Isolationism A multifarious issue that cuts across the two main parties, although it is more likely to find expression amongst those on the right of the Republican Party. Isolationism may be contrasted to the liberal interventionism of many Democrats. There is an old adage in the US; Democrats start wars and Republicans end them. In reality, the statement is not an accurate one (the two Bushes are the exceptions) – but the saying does have some degree of political currency. Democrats are more likely to believe that America’s military strength can be used to create a better world whereas isolationists in the GOP are more skeptical. The gloomy outlook of isolationists in the GOP – fearing the military and financial cost – contrasts with the more optimist outlook of liberal interventionism.

Issue ads Those advertisements that discuss a candidate by name with reference to a particular issue, but do not expressly advocate the election/defeat of a candidate. Issue ads fall outside of the FECA. In the case of FEC v. Wisconsin (2007), the Supreme Court ruled that issue ads could not be banned in the run-up to a general election or primary.

Issue network An alliance of various interest groups who unite in order to promote a single issue. They can be either domestic or international in scope.

Issue scale A survey response format in which respondents select their answers from a range of positions between two extremes. It can therefore be used to identify people’s ideological preferences.

Issue voters People who are well-informed about their own policy preferences and knowledgeable about the candidates—and use all of this information when they decide how to vote. They can see beyond the stereotypes presented by the media. It is often said that voters in Iowa and New Hampshire can see through the spin and ascertain who has the ability to become President.