Final answer:
Gerrymandering contributes to the incumbency effect by creating electoral districts that favor current officeholders, particularly in the House of Representatives, by including a majority of voters from their party, thus making reelection more likely.
Step-by-step explanation:
Gerrymandering is the manipulation of electoral district boundaries for political advantage. It significantly contributes to the incumbency effect, whereby current officeholders—most often House of Representatives members—have a higher probability of reelection. This is because gerrymandered districts often include a majority of voters who identify with the incumbent's political party, ensuring an electoral advantage. Additionally, gerrymandering reduces the incentive for politicians to cater to a broad range of views, which can lead to polarization as they serve only the dominant subset of the constituency.
Redistricting occurs every ten years after the U.S. Census when the allotment of House members to each state is determined. However, states may also redraw districts at other times. With the advent of advanced computing, the ability to collect data about potential voters, and the use of algorithms, map-making has become very precise, allowing politicians and interest groups to design districts that guarantee their electoral success and diminish the presence of moderates in Congress.
One key element in gerrymandering's potency is retrospective voting, allowing incumbents, who typically win reelection up to 90 percent of the time, to leverage their name recognition and voting records. The process often dissuades capable challengers from running and perpetuates the election of those currently holding office, largely because political action committees and interest groups prefer to donate to candidates most likely to win. The process can be so effective that it creates 'safe districts,' where general elections are non-competitive, and the real contest is within the primary of the dominant party.