Every 10 years — unfortunately, sometimes more frequently — legislative district lines are redrawn to balance population for demographic changes revealed by the census. What goes on is much more than a simple technical adjustment of boundaries, with ramifications that largely escape public notice.

Politicians often use redistricting as an opportunity to cut unfavorable constituents and potential challengers out of their districts. Barack Obama, for example, learned the rough and tumble of redistricting politics when Rep. Bobby Rush (D-Ill.) carved Obama's Chicago home out of Rush's congressional district after losing a 2000 primary challenge to Obama, then a state senator.

Incumbents can also use redistricting to move favorable constituents into their districts. Obama himself used the state legislative redistricting to extend his predominantly African American district north into a wealthy area of Illinois known as the Gold Coast. This new constituency allowed Obama to hone an effective biracial campaigning style that served him well when he ran for the U.S. Senate and the presidency.

Critically, these decisions are made with little or no public input or accountability. While Arizona and California are among the few states that give the public a chance to see and participate in how the boundaries are set, by using open redistricting commissions, most states gerrymander legislative lines behind closed doors. Figures from both major parties tilt the electoral playing field so much that one party is essentially assured of winning a given district, controlling the state legislature or winning the most seats in the state's congressional delegation. In other words, the democratic process is subverted. In this system, politicians select voters rather than voters electing politicians.

A 2006 Pew survey found that 70 percent of registered voters had no opinion about congressional redistricting. Among the few that expressed an opinion, some mistook the question to be about school districts rather than congressional districts.

For many reasons it has been hard to fault the public. An immense amount of population data must be sifted and then assembled, much like a giant jigsaw puzzle, to ensure that districts satisfy complex federal requirements relating to equal population and the Voting Rights Act, and varying state requirements that may include compactness and respect for existing political boundaries or communities. And access to these data and the software necessary to assemble and analyze them have long been out of public reach.

In the previous round of redistricting, according to a 2002 survey of authorities we conducted with our colleague Karin Mac Donald, most states did not provide any tools, facilities, dedicated assistance or software to support the public in developing redistricting plans. Many states failed to provide even minimal transparency by making data available, providing information about their plans online or accepting publicly submitted plans. Many redistricting authorities have not made firm plans to support transparency or public participation in the current round of redistricting.

In the coming year, however, technological advancements will enable anyone with a Web browser and an interest in how he or she is represented to draw district maps of his or her community and state that meet the same requirements as official submissions. Under the direction of scholars at the Brookings Institution and the American Enterprise Institute, and with consultation from an array of experts in redistricting issues, we have developed a set of principles for transparency and public participation. These principles have been endorsed by an array of stakeholders, including Common Cause and the League of Women Voters of the United States.

Americans will be able to participate directly in their democracy by offering plans to be compared with the politician-drawn maps. The public and even the courts will no longer have to accept that whatever is devised by politicians in the backroom.

The Wizard of Oz appeared powerful because he hid behind a curtain -- until it was pulled back. The time has come to pull back the curtain on redistricting. A good place to start is by passing Rep. John Tanner's Redistricting Transparency Act, which has 38 co-sponsors from both parties. If Congress will not act, state governments can follow the lead of the few states that provide for meaningful transparency and public participation. Failure to provide for transparency and public participation should be recognized for what it is: an obviously self-serving act, placing the interests of politicians above the public interest.