The results have varied, but supporters point to more competitive contests and new faces replacing incumbents as evidence of reduced gerrymandering, the delicate drawing of often misshapen districts to benefit one party or the other—or officeholders of either party seeking re-election.
In California, a 14-member citizen panel of Republicans, Democrats and people who are not affiliated with either party redrew the state's 53 congressional and 120 legislative maps in 2012. The realignment of political boundaries produced some of the most competitive congressional races in decades. Fourteen House incumbents either lost their seats or opted not to run under the new lines.
Arizona, Hawaii, Idaho, New Jersey and Washington also have set up commissions to redraw district boundaries after the new census every 10 years. A handful of others have formed panels to redraw only state legislature seats.
States set up their panels with different outcomes in mind, said Justin Levitt, an associate professor of law at Loyola University in Los Angeles, the creator of a website that tracks state redistricting efforts, http://redistricting.lls.edu/index.php.
Some states wanted to speed up an inherently political process often delayed for years in court; others sought to form districts that preserve like-minded voting blocs.
"There is no one perfect type of body," Levitt said. "I don't think that one state's model should just be dropped into another state. Every state is a little bit different, and so it makes sense to think of institutions that really fit into the nature of those states."
Washington state's redistricting process is "probably one of the most clean in the country. It has a track record of producing competitive state legislative districts and competitive congressional districts," said Todd Donovan, a Western Washington University political scientist. Races in two of the state's 10 U.S. House districts are expected to be competitive this year. The two leading political parties select four members and a nonvoting chair of the redistricting group.
Idaho also uses an "arms-length" political appointment process to select its bipartisan commission. Its two congressional districts were redrawn in 2011 on what has been a steadily westward-moving axis to accommodate growing Boise. The shift has had little impact in the heavily Republican state.
In California, the citizen panel held months of public hearings on how to draw the boundaries. Its members—five Republicans, five Democrats and four members with no political affiliation—are drawn from a pool that cannot include lobbyists, recent state officeholders or their staff.
"Having the lines drawn by citizens who had their eye on what was in the best interest of voters rather than politicians resulted in more choices for voters and more competition in our election process," said Kim Alexander, president of the California Voter Foundation, which supported a ballot initiative to create the commission in 2008 and expand its authority in 2010.
Arizona residents voted to give the job of redrawing legislative and congressional district lines to an independent bipartisan commission in 2000, but getting politics out of the process has proven elusive. The commission's first effort produced a decadelong court battle after Democrats argued that the five-member panel did not create enough competitive districts. That court challenge ultimately failed, but new maps drawn in 2012 are back in court.
Other states never intended to create more competitive districts.
New Jersey and Hawaii both choose politicians to sit on their commissions, which are "designed to take a little bit of the acrimony out of the process and to arrive at often a partisan compromise, but one that is often quite responsive," said Levitt.
In New Jersey, there is an inherent incentive to keep districts safe for incumbents and create a congressional delegation balanced between Republicans and Democrats, even though voters lean heavily Democratic in registration and presidential election voting.
Each party chooses six of the commission members and a 13th member is jointly chosen to serve as chair. When Democrats and Republicans reach an impasse on which map to use, the chair picks from their final proposals, as then-Chairman and former state Attorney General John Farmer Jr. did in 2012, choosing the Republicans' favored option.
Both choices were designed largely to maintain the status quo of relatively equal balance in the state's House delegation.
Associated Press writers Rebecca Boone in Boise, Idaho, Bob Christie in Phoenix, Oscar Garcia in Honolulu, Geoff Mulvihill in Trenton, N.J., and Manuel Valdes in Seattle contributed to this report.