Who draws the lines?

Different people are in charge of drawing the district lines in different states.

In most states, the state legislature has primary control of the redistricting process, both for state legislative districts and for congressional districts. 37 state legislatures have primary control of their own district lines, and 42 legislatures have primary control over the congressional lines in their state (including five of the states with just one congressional district).

In most of these states, district lines pass just like regular legislation, with a majority vote in each legislative chamber, subject to a veto by the Governor. Connecticut and Maine both require supermajorities, of two-thirds in each house, to approve a redistricting plan. And five of the states above -- Connecticut, Florida, Maryland, Mississippi, and North Carolina -- set district lines by joint resolution, without the potential for a gubernatorial veto.

Five of the states above -- Iowa, Maine, New York, Rhode Island, and Vermont -- appoint advisory commissions, to help advise the legislature about where the state legislative district lines should be drawn (there is a more detailed description of Iowa's special procedure here). Ohio (and as of 2011, Rhode Island) do the same for congressional lines. (In most states, legislative committees draft initial redistricting plans, just like they draft most legislation. But in these states with advisory committees, non-legislators are also invited to formally participate on the initial drafting body.)

The legislature is not bound by what these advisory commissions recommend, but because the legislative leadership usually has a role in appointing the commission's membership, the commission's advice tends to influence the legislature's final decision substantially.

In Virginia, the governor issued an executive order in 2011 creating a similar advisory commission for his own benefit, but it is not yet clear whether the legislature will pay any special attention to this commission's input.

If advisory commissions influence redistricting maps before they go to the legislature, backup commissions have their influence afterward. In seven of the states above -- Connecticut, Illinois, Maryland, Mississippi, Oklahoma, Oregon, and Texas -- there are special backup procedures to draw state district lines if the legislature does not successfully pass a plan. (Connecticut and Indiana use backup commissions for congressional districts.) Usually, a specific deadline in the state constitution triggers the backup commission's work.

These backup commissions all look a bit different. In Maryland, redistricting falls to the Governor's preferred plan if the legislature fails to act. In Oregon, the Secretary of State is the backup actor. In Connecticut and Illinois, the backup commission is composed of members selected by the legislative leadership. In Mississippi and Texas, the backup commission includes specific statewide elected officials, like the State Treasurer or state Attorney General. In Oklahoma, a 2010 citizen's initiative blended these models, establishing a backup commission composed of the Lieutenant Governor, and several members selected by the majority party's legislative leadership and the Governor.

In all of the states above, the legislature is primarily in charge of redistricting. Elsewhere, some other entity draws the lines. Seven states -- Arkansas, Colorado, Hawaii, Missouri, New Jersey, Ohio, and Pennsylvania -- draw state legislative districts with so-called "politician commissions," where elected officials may serve as members. (Hawaii and New Jersey use politician commissions for congressional districts.)

Each, again, is a bit different. In Arkansas and Ohio, specific elected officials have designated seats on the commission. In the other states, the legislative or party leadership nominates commissioners, usually with balanced numbers from each party, and sometimes with a role for the Governor or Chief Justice of the state Supreme Court to select nominees or appoint additional members of the commission.

The remaining states -- Alaska, Arizona, California, Idaho, Montana, and Washington -- all draw both state and federal districts using an independent commission, with regulations limiting direct participation by elected officials. (Alaska and Montana currently have only one congressional representative, and do not need to draw congressional lines.)

Members of these commissions are neither legislators nor public officials. Each state also bans commissioners from running for office in the districts they draw, at least for a few years after the commission finishes its work.

Some of the states further limit commission members' link to the legislature: Arizona and California, for example, also bar legislative staff from serving on the commission; California, Idaho, and Washington bar lobbyists from serving on the commission as well.