DES MOINES - Iowa's elected officials are looking ahead to how this year's census will reshape the state's political landscape.

The biggest change will be the loss of one of Iowa's five seats in Congress.

Lawmakers are expected to approve a new map next year, ahead of the 2012 elections, that will draw lines for Iowa's congressional districts as well as Iowa House and Senate districts.

Completed every 10 years, redistricting can lead to a wave of retirements by elected officials or showdowns between incumbents paired in the same district.

"If history has shown us anything in Iowa, it's that especially at the congressional level, legislative redistricting is very unpredictable," said Matt Strawn, chairman of the Republican Party of Iowa.

The way Iowa approaches the task adds to the unpredictability. Iowa's nonpartisan Legislative Services Agency is charged with drawing maps armed with the latest data from the U.S. Census Bureau.

Ed Cook is part of the three-person agency team that completes redistricting proposals. He says the group works to maintain complete secrecy until the map is released to the Legislature next year and will try to find a location outside the Capitol to work.

"It just eliminates any perception that there's any kind of collaboration with the Legislature at all. It's never been an issue," Cook said.

Once the first plan is released, lawmakers can approve or reject the map, taking a gamble they will like a second plan drawn by the Legislative Services Agency better. If they reject the second proposal, they will get a third plan they can amend.

With Iowa expected to lose a congressional seat after this year's census count, the makeup of the Legislature next year could be key in approval of new districts. A Democratic majority could help protect Democratic incumbents in Congress or the Legislature, while a GOP majority could lead to a map more favorable for Republicans.

Leaders on both sides of the aisle praise Iowa's process. Senate Minority Leader Paul McKinley, R-Chariton, calls redistricting healthy and thinks Iowa's system is one of the best.

"The restrictions on how you can divide up these districts is pretty well-prescribed," he said.

House Speaker Pat Murphy, D-Dubuque, stresses the nonpartisan nature of the process since lawmakers are not in charge of drawing the maps.

"A lot of it really is taken out of our hands," Murphy said.

Murphy compares redistricting to term limits, since lawmakers cannot draw lines that favor themselves. He points to a large degree of turnover in the Iowa Legislature in the 2002 election cycle after districts were redrawn and sees the potential this time.

"You have the chance for a huge turnover come 2011, and I think everybody around here believes that that's a possibility," Murphy said.

House Majority Leader Kevin McCarthy, D-Des Moines, ran for and won an open seat created by redistricting, joining the Legislature with a large freshman class after the 2002 election. He praises Iowa's system of redistricting because he said the majority party has little or no influence.

"If you talk to most reasonable people that are involved in the process on either side of the aisle, it is probably the most clean, most fair redistricting system we have in the entire country," McCarthy said.

Senate Majority Leader Mike Gronstal, D-Council Bluffs, said in some states, the party in control can "stack the deck" with creative mapping, making changes that are nearly locked in for a decade.

But Gronstal points to the last two decades in Iowa as proof that Iowa's system is balanced.

In the 1990s, Democrats were in control during the redistricting process but lost control of the Legislature later in the decade. Republicans who maintained a legislative majority during redistricting in 2001 lost majorities in later years as well.

Gronstal hesitates to make predictions on Iowa's congressional maps this time around, because the population requirements for equality are so precise.

"It's the luck of the draw as to whether you pick Boone County to add to a congressional district or Greene County to add to a congressional district," Gronstal said.

The last time Iowa saw redistricting in 2001, majority Republicans rejected the first proposed map, saying the population variances in districts were too large.

That map placed former GOP congressmen Jim Leach and Jim Nussle in the same eastern Iowa district and pitted 70 incumbents in the Iowa Legislature against each other.

The second map, which ultimately was approved, still put Leach and Nussle in the same district, and prompted Leach to move from Davenport to Iowa City to run from that district.

Drawing new congressional and legislative districts is an exacting science made easier by specialized computer software.

In the last redistricting, congressional districts had less than 600,000 people, Cook said. If Iowa were to lose a district as is expected, Cook believes the districts would have about 750,000 people, but said they won't know until they get the census data.

Those drawing congressional districts are looking to ensure "one person, one vote," with districts as close to the ideal population as possible.

"A shift of no more than 2,000 people throughout the state can radically alter how a congressional plan is going to look, because you want to get the deviation within under 100," Cook said.