Every ten years, state legislatures re-draw their boundaries. They do this after the census has been evaluated to make sure that congressional seats are apportioned in a "fair" way amongst the people of the state.
There are four basic goals that, for the most part, should be achieved when creating a redistricting plan. A general idea of these goals are (1) the districts created should form a contiguous territory, (2) the districts should tend to be compact (avoiding the conflicting concept of gerrymandering), (3) boundaries between districts should follow major streets or other well-defined boundaries, (4) the census block cannot be split. Although each state does usually set their own specific goals, they all tend to be very similar, with just minor differences.
The Constitution lets the states draw their own districts, but the Federal Courts have strict rules about who approves them. Courts can approve, reject, and sometimes create drawn districts (Engstrom 2002).
CAIN_2000
ours is a two-party system (notes)
The Redistricting Process: The Legal, Practical an...The method that the state uses to draw these districts, directly affect the competitiveness of the elections. The competitiveness can be looked at as the way both parties have a somewhat "equal" opportunity to have a positive ending result in an election. There are three different types of redistricting methods - legislative, commissions, and plans drawn by the court.
Redistricting is one of the main factors in causing an increase in the incumbents' advantages, especially in congress. Tufte (1973) noted a decline in competition in the first election that was preceded by a redistricting cycle; he argued that incumbents influence the process of redistricting to save their seats. Ehrenhalt (1983) also stated that the incumbent is given the advantage when it comes to redistricting because he has more time to present himself to what could be his new constituency. Abramowitz (1983) noted that Democratic candidates had...