POPULATION shifts require that congressional districts be redrawn after each census.

Historically, the redistricting process has been overseen by elected officials who have distorted the process to favor incumbents through gerrymandering, which occurs when legislators draw up districts in a partisan manner so as to give their own party's incumbents an advantage.

Instead of voters' choosing who they want in office, the politicians are choosing who their voters will be. Gerrymandering often creates safe seats for districts with enough Democrats or Republicans to make a real contest unlikely.

Most Americans don't realize the negative impact that many years of gerrymandering has had on the ability of Congress to accomplish our nation's common goals. The only serious challenges to the incumbents holding safe seats come from the extreme wings of their own parties. That encourages elected officials to pander to the most extreme elements in their party while ignoring the political center.

In many places, primaries are now deciding the November elections. The outcome is a polarized political atmosphere where many members of Congress aren't willing to work across party lines for fear of alienating the base of activist voters in their own party. In 2006, 86 percent of House members had no serious competition and nearly 95 percent of all incumbents won, a so-called "wave election."

The damage to our democracy caused by gerrymandering is chronicled in "Gerrymandering," a documentary to be released in 2010.

And the Annenberg Center at the University of Southern California has produced the appropriately named "Redistricting Game," while an outfit called Fair Vote has a game called "Redistricting Roulette." Both are entertainments with the serious purpose of educating citizens about how redistricting affects the democratic process and how adjusting district lines can have a vast impact on who gets elected.

But there is hope.

Nonpartisan redistricting overseen by independent bipartisan commissions in each state offers a much better alternative to the current system of letting elected officials redraw the lines for partisan gain.

Rep. John Tanner of Tennessee and Sen. Tim Johnson of South Dakota, both Democrats, have introduced "The Fairness and Independence in Redistricting Act" (H.R. 3025 and S.B. 1332), which would require all states to use independent commissions and follow "traditional redistricting principles."

Both bills call for an independent commission made up of bipartisan appointees and are supported by nonpartisan "good government" groups that include Americans for Redistricting Reform, the League of Women Voters and the U.S. Public Interest Research Groups.

A SIMILAR bill was introduced in the 109th Congress but didn't pass.

Now is a key time to make the needed changes before the 2010 census figures are released (which will trigger redistricting). Experts predict that population shifts since the last census will result in seven states losing seats and 10 gaining seats.

Call or write to your senator and congressman today to express your support for the Fairness and Independence in Redistricting Act.

Redistricting reform isn't a headline-grabbing issue, but it's critical for restoring a healthy democracy.

Ellen Kadransky is a political activist in Upper Darby. E-mail