A divided Congress returned to work this week amid national unhappiness over partisan stalemate. Meanwhile, back home in most states — including Maryland and Virginia — Democrats and Republicans alike were busy redrawing congressional and state legislative districts in ways that usually ensure the gridlock gets even worse.

It happens every 10 years, when voting districts are adjusted to reflect population figures from the latest census. The two main political parties control the process in most places and hope the public doesn’t pay too much attention.

There’s little or no effective input from independent outsiders who would put fairness or other civic values ahead of narrow political self-interest.

“It’s a pox on both their houses. It’s not about good government. It’s not about democracy. It’s about control,” said Donald F. Norris, chairman of the department of public policy at the University of Maryland Baltimore County.

In Maryland, the all-powerful Democratic Party plans to fiddle with the map to try to boost its majority in the U.S. House delegation from 6-2 to 7-1. That would leave the GOP with only one-eighth of the seats in a state where more than two in five voters picked Republican Bob Ehrlich for governor in 2010.

Virginia Republicans — who are dominant, but not totally — hope to lock in an 8-3 congressional majority. Success would mean they keep 73 percent of the seats, after receiving only 54 percent of total votes in House races in 2010.

The political parties achieve these tricks by gerrymandering, or drawing bizarrely shaped districts designed to protect incumbents or unseat rivals. They do so regardless of whether the lines reflect county or municipal boundaries or whether they break up such groups as minority populations or rural voters.

“It’s very difficult to completely extract politics from anything. But I think we could do a far better job of preserving geographical communities of interest and make the lines more understandable to voters,” said Bob Holsworth, who chaired Virginia’s bipartisan redistricting commission.

The General Assembly set aside the group’s recommendations in the spring, choosing instead to put forth competing partisan proposals.

The practice tends to drive politicians to ideological extremes. The parties safeguard incumbents by creating districts that are so lopsided that politicians needn’t worry about the other side in a general election. Instead, they end up focusing on the party primary and cater to the base.

“It often becomes true that the real risk that an incumbent faces is not being beaten by the other party, but being challenged from within the party, in all likelihood by someone who’s more extreme,” said lawyer Paul Smith, a partner at Jenner & Block and co-author of a redistricting manual published by the American Bar Association.

An important byproduct is a chronic lack of ideological give-and-take in campaigns. One party barely bothers to make an effort in many races, because the result is preordained.

Stephen Shapiro, a local Democratic Party official in Bethesda, testified to that at a redistricting hearing in Rockville last month.

“In some respects, the current congressional districts have made my job as a Democratic precinct chair too easy. My candidates always win — at least in the general election,” Shapiro said. “I am concerned that it is decreasing debate and turnout. Most of the competition is in our primary elections, where there is relative agreement among most candidates.”

Quentin Kidd, a political science professor at Christopher Newport University in Newport News, estimated that three-quarters of seats in the Virginia House of Delegates are noncompetitive. “That can’t be good for the democratic process. There’s really no debate over policy, no clash of ideas going on,” he said.

None of this will change until the public insists on it. In U.S. House redistricting, both national parties are so keen on trying to secure an advantage ahead of 2012 that other concerns are ignored.

“At the moment, the pressure from on top is so great on Republican- and Democratic-controlled states to bolster the party numbers that all other state-based or population-based interests are being pushed to the back burner,” said Todd Eberly, a political science professor at St. Mary’s College.

It’s almost certainly too late to fix this for the current decade. The public should start now to demand a fairer, more neutral method after the 2020 Census.

I discuss local issues at 8:51 a.m. Friday on WAMU (88.5 FM).