Legislative redistricting is the process of redrawing the boundary lines of legislative districts. The purpose of legislative redistricting is to ensure that each person is equally represented in our democracy by the creation of districts that are as equal in population as practicable, consistent with other state constitutional parameters, so as to achieve the principle of “one person – one vote.” The legislative redistricting process must occur every ten years, at the beginning of each decade, after a state officially receives the results of the federal decennial census, which provides the demographic and geographic data from which the districts are created.

Before legislative redistricting can occur in any state, the federal decennial census of the United States must be taken.  The Secretary of the federal Department of Commerce and its Bureau of the Census are required to take a decennial census of the population as of the first day of April of each year ending in zero, in such form and content as the Secretary may determine, and to complete the tabulation and report the results, by state, to the President of the United States by December 31 of the same year. 

The Secretary is to report the census results no later than April 1 of the following  year to each state's "Governor...and to the officers or public bodies having responsibility for legislative apportionment or districting." The reports contain the population data for various geographical areas within the state, including the smallest area, the census block.

Census data is the basis for creating legislative districts.  However, the United States Constitution leaves it to each state to establish its own method of redrawing legislative boundaries at the start of each decade.  In the majority of states, the legislative district plan takes the form of a bill passed by the Legislature and signed into law by the Governor.  In over a dozen other states, responsibility for legislative redistricting is assigned to a group other than the legislature.  Such is the case in New Jersey, where a plan is created by an Apportionment Commission provided for in the New Jersey Constitution.

In 1966, the State Constitutional Convention recommended, and a majority of voters approved at the general election in that year, an amendment to the New Jersey Constitution shifting the responsibility of drawing the legislative districts from the Legislature to an Apportionment Commission.

Under Article IV, Section III, paragraph 1, the State Constitution provides that the Apportionment Commission is to be composed of 10 members with five each appointed by the State chairmen of the two largest political parties.  The appointments must be made with consideration given to the representation of the various geographical areas of the State.  They must also be made by November 15 of the year in which the census is taken and certified to the Secretary of State on or before December 1 of that year.

The Apportionment Commission is directed to certify a redistricting plan within one month of receipt by the Governor of the census, or on or before February 1st of the year following the year in which the census is taken, whichever is later.

Under Article IV, Section III, paragraph 2, the State Constitution further provides that if a majority of the commission is unable to agree on a plan within this period, it must so certify to the Chief Justice of the New Jersey Supreme Court, who will then appoint an eleventh member.  With this new member, the reconstituted commission has one month to certify a plan to the Secretary of State.  Under Article IV, Section III, paragraph 3, the State Constitution provides that, once established, the plan remains unaltered until the following decennial census of the State is received by the Governor.

The time frame for legislative redistricting is tight.  The first legislative elections in a new decade and redistricting both occur in the first year thereof ending in one.  All petitions of nomination of candidates for legislative office are to be filed no later than the 57th day before the primary election, which usually occurs during the second week of April.

Although the official deadline for the Census Bureau to provide data to the states is April 1 of the year ending in one, the bureau has sought to help the State meet its deadlines by providing census data by late January or early February. This allows the commission time to accomplish its task and the candidates for office to know the new boundaries of their district sufficiently in advance of the filing deadline.

The process of legislative redistricting must comply with a range of redistricting principles that have been established over time through constitutional provisions, laws, and court decisions. Among the range of applicable redistricting principles that must be followed in New Jersey, the 1966 Constitutional Convention attempted to end the common practice of drawing district lines for partisan advantage, known as gerrymandering, by imposing several standards, or guidelines, for drawing equitable districts.  These standards have been modified by subsequent court rulings.

Article IV, Section II, paragraph 3 provides that Assembly districts are to be:

"composed of contiguous territory, as nearly compact as possible and equal in the number of inhabitants as possible, and in no event shall each such district contain less than eighty percent nor more than one hundred twenty percent of one-fortieth of the total number of inhabitants of the State....Unless necessary to meet the foregoing requirements, no county or municipality shall be divided among Assembly districts unless it shall contain more than one-fortieth of the total number of inhabitants of the State...."

Other redistricting principles must also be followed, in accordance with established constitutional provisions, laws such as the federal Voting Rights Act of 1965, and a significant number of court decisions.