Why are incumbent members of Congress much more likely to be reelected than defeated by their challengers?
The success rates for House and Senate incumbents seeking reelection1 slowly increased, on average in each election year between 1946 and 2024, from approximately 60% for both House and Senate incumbents, to approximately 95% for congressmembers and 85% for Senators.2 Political scientists who study this phenomenon3 identify several factors, known as incumbency advantage, that, when taken together, provide an explanation for the phenomenon. The factors and how they benefit incumbents are discussed below.
The first and foremost of all incumbent advantages is name recognition. Few voters are likely to cast a ballot for candidates completely unknown to them, whereas incumbents immediately begin a reelection campaign as known quantities to most voters. (The means by which incumbents retain high name recognition appear below.) Challengers, in contrast, must establish sufficient name recognition to be credible with voters, either by attracting attention without spending money (ie, free media — discussed below) or by raising and spending sufficient funds to become as well-known as their incumbent opponents, which is extremely difficult for most challengers.4 When the opposition party recruits candidates to challenge incumbents, they often seek individuals who are already well known to voters. For example, during his time as Penn State University’s head football coach, Joe Paterno was approached several times by the Republican Party to run for governor. “JoPa” was an admired and widely recognized across the Commonwealth, making it far easier to market him as a candidate than a person with little to no name recognition.
Gerrymandering also contributes to incumbency advantage. (See the entry on “apportionment, redistricting and gerrymandering” for a complete discussion.) When an incumbent runs in a gerrymandered district, the incumbent is likely doing so from a safe seat, that is, a district in which the incumbent, or prior candidates from the incumbent’s party, have won the seat with 55% or more of the votes cast.5 As the opposing party’s candidate, the challenger confronts an electorate composed of a majority of the incumbent’s party before the campaign begins. Research confirms that gerrymandered districts also discourage viable candidates of the opposition party from challenging incumbents, which results in incumbents with very safe seats ( ≥ 70% vote margins) running unopposed.6
Raising money to sufficiently fund a viable congressional campaign is difficult. The process takes time, knowledge of donors capable of making large contributions, and a willingness to ask strangers to donate to one’s campaign. Incumbents are in a much better position to engage in fundraising than their challengers, because they have time (two full years for a House member and six for a Senator), a donor list constructed over many campaigns, and experience asking for money from strangers. According to Kernell and Jacobson’s research, donors act strategically.6 They assess each candidate’s probability of victory and make their donations to the candidate most likely to win. Usually that candidate is an incumbent, because donors are aware of the high reelection rate of incumbents. For a challenger to approach a 50% chance of defeating an incumbent, the challenger must raise and spend at least as much as the incumbent; very few challengers can meet these thresholds, giving the advantage to the incumbent yet again.7
Incumbents demonstrate their effectiveness as representatives and
Senators while also reinforcing their name recognition through
constituent service, of which there are two types.8 The
first is individual constituent service. Every member of
Congress has staff dedicated to responding to constituent
concerns. When constituents contact their congressmember
and Senator, whether to complain about a policy matter or to request
assistance with a government agency (eg, difficulty in
getting V.A. benefits, problems with Social Security or
Medicare payments, accessing SNAP benefits, or even
dealing with problems that arise from a state or local municipal
government), staff devote considerable time and effort to resolve
the problems in ways that benefit the constituents. When
the constituents’ problems are fixed, they are very likely to not
only view the incumbent favorably, but also share their good news
with friends and family, thereby spreading the incumbent’s name in a
positive way.9
The second type of constituent service is district-wide
service, in which an incumbent directs federal funds to the district
through an earmark in an appropriation (spending)
bill,10 and/or assists the
district in gaining a federal grant for a special project.
Federal funding spent in a state or district usually lessens or
eliminates the state’s or local government’s contributions for these
projects. These projects, in turn, often bring jobs to the state or
municipality. Incumbents claim credit for the grants and
federal spending, enhancing their name recognition, and gain free
media when press conferences are held to announce these
achievements.11
Constituent service work is totally unavailable to
challengers. They can, however, attempt to discredit an
incumbent’s claim to have personally been responsible for bringing a
grant or federal spending, or challenge the value of the grant or
federal money to the state or district.
Incumbents begin each new campaign with experienced and knowledgeable staff who, among other things, know the district’s voters, the issues that are most important to the voters, and the best ways to market their candidate to the voters. House and Senate staffers are paid by Congress. As federal employees, they are obliged to work on tasks related to their employers’ official duties, such as researching legislation, dealing with constituent issues, etc. It is illegal for them to engage in partisan political activities at the same time. However, any staffer may take a leave of absence for a campaign’s duration to work only on the campaign and return when the election ends. As a campaign worker, the individual is paid from the campaign’s funds.12 Challengers, in contrast, must build a campaign team, often from nothing. Finding experienced people who have worked successful campaigns takes time; moreover, attracting them to a potentially losing campaign — remember incumbent reelection rates — takes money. Veteran campaign workers are rare and expensive. The advantage here again goes to the incumbent.
Free media refers to any media coverage, but particularly news reporting, that a candidate receives but does not pay for. The antithesis of free media is paid media, more commonly known as advertising. Incumbents have a relatively easier time gaining free media. A representative or Senator may call a press conference at any time to announce some accomplishment or to take a stand on some current event, affording the incumbent free press coverage. (Such free media ties into an incumbent’s district-wide constituent service and credit-claiming.) An incumbent’s campaign events are much more likely to receive wider and more extensive coverage by reporters than those of a challenger. Free media further establishes an incumbent’s name recognition that contributes to the incumbent’s advantage.
Only incumbents have access to the franking privilege: a congressperson’s ability to send mail to constituents for free. Instead of a stamp, the member’s signature appears where the stamp is placed. The privilege first appeared in 1775 as a means for congresspeople to communicate with their constituents. Congress passed a law in 1789 making the rule permanent, and in the 1970s, Congress added limits on the privilege to prevent incumbents from using it during campaigns: franked mail could not be sent within 90 days of a congressional election. This did not stop members from mailing materials to constituents informing them of their member’s accomplishments for the district 91 days before the election. Though fewer people today depend on the US mail for their information, franked mail sent over two-year House, and six-year Senate terms further establish the members’ name recognition with their constituents.
In the 21st Century, when incumbents are defeated, it is usually in a primary not a general election. Incumbents, even in safe seats, fear being primaried by a person either more conservative or more liberal than the incumbent. Primary challengers, nonetheless, face the same uphill battles that challengers in general elections face: incumbency advantage.
When incumbents lose, whether in a primary or general election, the reasons are likely to be one or more of the following factors: scandals of a personal (viz. sexual, marital, etc.) or professional (business misdeeds, ethical problems, etc.) nature; agism, should the incumbent appears to be too frail or mentally unfit to continue to serve; and losing touch with the district or state, that is, the incumbent appears to be spending too much time in Washington rather than with constituents at “home.”
- Some incumbents decide to retire, seek a different elected office (eg, Senator, governor), or are appointed to a position in a presidential or gubernatorial administration. These incumbents are not included in the discussion here. ⇧
- See graphs of incumbent advantages for the House and Senate since 1964 at Open Secrets. ⇧
- See a) Erikson, Robert S. 1971. “The Advantages of Incumbency in Congressional Elections.” Polity 3:395–405; b) Ferejohn, John A. 1977. “On the Decline in Competition in Congressional Elections.” American Political Science Review 66:1234-55; c) Jacobson, Gary. 1987. “The Marginals Never Vanished: Incumbency and Competition in Elections to the US House.” American Political Science Review 31: 126-411; d) Mayhew, David. 1971. “Congressional Elections: The Case of the Vanishing Marginal.” Polity 6:295-317; e) Payne, James L. “The Personal Electoral Advantage of House Incumbents.” American Politics Quarterly 8:375-398; f) Collie, Melissa. 11981. “Incumbency, Electoral Safety and Turnover in the US House of Representatives, 1952-1976.” American Political Science Review 75:19-31; g) King, Gary; Gelman, Andrew. 1991. “Systemic Consequences of Incumbency Advantage in US House Elections.” American Journal of Political Science 35: 110-38; h) Cox, Gary W.; Katz, Jonathon N. 1996. “Why Did the Incumbency Advantage in US House Elections Grow?” American Journal of Political Science 40: 478-497. ⇧
- See a) Jacobson, Gary C. 1980. Money in Congressional Elections. New Haven: Yale University Press; b) Herrnson, Paul; Panagopoulos, Costas; Bailey,Kendall. 2020. Congressional Elections: Campaigning at Home and in Washington, 8th ed. Washington, DC: Congressional Quarterly Press; c) Latus Nugent, Margaret, ed. 2019. Money, Elections, And Democracy: Reforming Congressional Campaign Finance. New York: Westview Press; d) Parker, David C.W. 2008. The Power of Money in Congressional Campaigns, 1880–2006. Norman: University of Oklahoma Press; and e) Francia, Peter L.; Green, John C.; Herrnson, Paul; Powell, Lynda W. 2003. The Financiers of Congressional Elections: Investors, Ideologues, and Intimates: Power, Conflict, and Democracy: American Politics Into the 21st Century. New York: Columbia University Press. ⇧
- Political scientists settled on “55% and larger victory margins” as the “definition” of a safe seat, because it reflects a comfortable victory margin for the winning candidate: >55% versus <45% for the losing candidate. (In multiple candidate elections, the defeated candidates share the remaining votes cast.) A marginal district is one in which the winning candidate receives between 45% and 54% of the votes cast, again because of multiple opposition candidates. There have been and continue to be incumbents who achieve reelection in marginal districts, but at some point, they are either defeated, or their districts are redrawn to become safe seats. ⇧
- Kernell, Samuel; Jacobson, Gary. 1983. Strategy and Choice in Congressional Elections. New Haven: Yale University Press. ⇧ ⇧
- See the sources listed in note 4 for further reading. ⇧
- See Cain, Bruce; Ferejohn, John; Fiorina, Morris. 1987. The Personal Vote: Constituent Service and Electoral Independence. Cambridge: Harvard University Press, and Johannes, John. 1984. To Serve the People: Congress and Constituent Service. Lincoln: University of Nebraska Press. ⇧
- See Fiorina, Morris. 1977. Congress: Keystone of the Washington Establishment. New Haven: Yale University Press. ⇧
- Such appropriations bills were once derogatorily called pork barrel spending bills, because the bills contained money for almost every district and state. They were considered a waste of federal dollars. The term “pork barrel” can be traced to the practice of delivering barrels of salted pork to enslaved people working in the fields. A political cartoon from the late 19th Century showed congressmembers as pigs rushing to the barrels of federal funds to feed. The caricature captured the public’s imagination. Contemporary examples of pork barrel projects, except in the eyes of the recipients, include Boston’s Big Dig project (1982 to 2007) that placed miles of highways in the city underground, and 2023’s $223 million Bridge to Nowhere that connected two small towns in Alaska. ⇧
- See Fenno, Richard F. 1978. Home Style: House Members in their Districts. New York: Longman Publishing. ⇧
- Staff members may also volunteer to work on their members’ campaigns during their vacations, free time, or when not working as a federal employee. These same rules apply to House members and Senators: it is illegal for them to use federal resources, such as their offices, automobiles paid for by the government, paper, pencils, computers, etc., for their campaigns. But, like staffers, if members leave their offices and go to their campaigns’ office at any time, they may make phone calls to raise money, meet with prospective donors, and, with today’s technology, hold Zoom political rallies. As long as neither the staffers or members are not receiving federal pay or using federal resources when they engage in partisan activities, it is legal for them to do so. ⇧