Four of the most recent GOP retirements - which reach from the conservative heartland of southeast Alabama all the way to the college precincts of Columbus, Ohio - offer a telling preview into the battle for the House next year.
Both parties believe these newly open seats are winnable. And all feature highly touted candidates who have already announced or are actively considering candidacies.
Here is a closer look.
Minnesota's 3rd: This suburban Minneapolis district held by retiring Rep. Jim Ramstad is emblematic of the type of seat Republicans need to hold - both to keep alive any hopes of taking back control of Congress and to have a shot at winning the White House.
The district, like many in the suburbs, has a tradition of economic conservatism and social liberalism. Ramstad reflected the moderate zeitgeist of the district, always winning with at least 64 percent of the vote.
Republicans face a delicate task in nominating someone who can fill the seat, as they have to navigate between their party's conservative base, which chooses the nominee at a districtwide convention in May, and the district's history of electing socially moderate Republican nominees.
On the GOP side, former House Majority Leader Erik Paulsen - dubbed an establishment conservative by state politicos - looks like the early front-runner if he opts to run.
But his biggest challenge could come from state Rep. Joyce Peppin, a movement conservative who has drawn opposition from both Democrats and moderate Republicans.
"She's in the Bachmann mold," said Minnesota lobbyist Paul Cassidy, referring to the culturally conservative lawmaker Rep. Michele Bachmann, from the neighboring congressional district.
Two women lead the list of likely Democratic nominees. State Sen. Terri Bonoff has announced her campaign and has a record of winning a traditionally Republican legislative seat.
In her Senate campaign, she won the endorsement of both labor and the state Chamber of Commerce - which is unusual in Minnesota politics.
"I have demonstrated that I am that type of representative who does reflect the values of the district. I am a fiscal moderate in belief and voting record," Bonoff said.
State Rep. Melissa Hortman, who is eyeing the race, represents more of a working-class part of Hennepin County and has close ties with labor and the progressive movement.
EMILY's List, which supports and funds Democratic women candidates who support abortion rights, views both candidates favorably.
As one Democratic operative put it, Minnesota's 3rd is a "classic EMILY's List district," given its high representation of women in the legislature and its liberal mentality on social and cultural issues.
Illinois' 11th: Of the three open seats in Illinois, this is the one that Republicans are most concerned about.
The fast-growing district, located in Joliet, gave President Bush 53 percent of the vote in 2004 but is trending independent as more unaffiliated voters are moving in.
Retiring Rep. Jerry Weller always managed to rack up decisive victories there, even as his Democratic opponents raised issues about his personal background.
The Democrats' dream candidate is state Senate Majority Leader Debbie Halvorson, who met with campaign committee officials and EMILY's List recently.
Party sources suggested that she was leaning against running for Congress so she could move up further within state legislative leadership, however.
"It's hard to be one of 435 when you can be the first woman state Senate president in Illinois," said a Democratic Illinois operative.
If she doesn't run, other potential Democratic candidates include last year's nominee, John Pavich, community college president Jerry Weber and former state Rep. Mary Kay O'Brien.
State Sen. Christine Radogno iemerging as the early odds-on favorite among Republicans.
Despite losing the state treasurer's race last year, she has received positive publicity for her moderate credentials and work on the state budget.
Republican insiders believe a pro-abortion-rights woman with legislative experience, such as Radogno, would be an ideal fit for the district.
Joliet Mayor Art Schultz, New Lenox Mayor Tim Baldermann and bank president James Roolf are also considering running on the Republican side.
Alabama's 2nd: Rep. Terry Everett's retirement opens up a seat that is in the heart of the rural South, where the Republicans still hold overwhelming electoral advantages.
Even George C. Wallace, son of the state's former governor, couldn't defeat Everett when he ran against him as a Democrat in 1992.
But Democrats are hopeful that they can be competitive in Everett's seat.
They cite the district's growing African-American population and evacuees from New Orleans as altering the district's demographics enough to make it competitive - with the right candidate.
They are hoping that candidate is Montgomery Mayor Bobby Bright, who has helped revitalize the city's downtown since taking over in 1999.
He is registered as an independent. But in a congressional election where national issues are front and center, it will be difficult for Democrats - including Bright - to distance themselves from the party's platform on hot-button social issues, which don't play well in small-town Alabama.
In a 2005 interview with the local business journal, Bright hinted that he had congressional aspirations. "My dream is to represent Alabama or a segment of Alabama in Washington, D.C.," he said.
All four potential GOP candidates have records as strong conservatives, so the primary will hinge more on geography than ideology.
The district's two population bases are in the Montgomery suburbs and the city of Dothan in its southeast corner.
State Rep. Jay Love and state Sen. David Grimes, who both hail from Montgomery, have already announced their candidacies.
State Rep. Greg Wren is forming an exploratory committee.
One other potential candidate, state Sen. Harri Anne Smith, is from Everett's hometown and said she will soon make a decision.
Ohio's 15th: Since Rep. Deborah Pryce's retirement, Republicans have been scrambling to find a candidate willing to run against the presumptive Democratic nominee, Franklin County Commissioner Mary Jo Kilroy.
They haven't had much success.
At least four candidates have opted out of the race. An African-American Baptist pastor, Aaron Wheeler, announced his candidacy, but he is viewed as a long shot.
Even though Pryce won reelection with healthy margins until last year, the Columbus-based district has been quite friendly to Democrats in recent years.
Young college-educated voters have been swarming into the area, giving the district a more liberal flavor.
Despite the GOP woes, Kilroy still has to demonstrate she can raise money and attract voters beyond her liberal base.
Although she was running in a very favorable environment - both statewide and nationally - she won only 49 percent of the vote against Pryce last year. And she got off to a slow fundraising start, largely because she faced a primary opponent for much of the year.