Incumbent: Deborah Pryce , Republican

Kilroy, an elected commissioner in the county that envelops Columbus, narrowly lost to veteran Republican Pryce in 2006 and never really stopped running. Pryce’s retirement after 16 years in the House means that Kilroy will be facing a different Republican opponent this time: state Sen. Steve Stivers, who started his campaign much later than Kilroy but has done well enough at fundraising to edge into this list as Number 10 (see below).

CQ rating: No Clear Favorite

3) Doug Ose, Republican, California’s 4th ($845,000)

Incumbent: John T. Doolittle , Republican

Ose represented suburbs of Sacramento in an adjacent district from 1999 through 2004. He’s now seeking a comeback in the Republican-leaning northeastern California district where retiring nine-term Doolittle long dominated — until questions about his past links to convicted lobbyist Jack Abramoff nearly cost him his seat in the 2006 election.

Ose is dipping deeply into his personal accounts to help finance his bid this year. One of the more moderate Republican members during his previous House tenure, he is opposed in the campaign for the June 3 Republican primary by state Sen. Tom McClintock, a conservative who has backing from the Club for Growth, a group that backs candidates who endorse fiscal restraint, lower taxes and free trade. Two lesser-known Republicans are running.

The presumed Democratic nominee is Charlie Brown, the retired Air Force lieutenant colonel who nearly defeated Doolittle in 2006 and who planned for a rematch this year. With $591,000 left to spend as April began, Brown finished just outside this “Top 10” list.

CQ rating: Leans Republican

4) Linda Stender, Democrat, New Jersey’s 7th ($845,000)

Incumbent: Mike Ferguson , Republican

Stender, a member of the New Jersey state Assembly, planned to wage a second campaign against Ferguson, to whom she lost by just 1 percentage point in 2006. But Ferguson surprisingly announced last November that he would retire from Congress instead of seeking a fifth term. Stender is the lone Democratic candidate in this year’s race. The Republicans, have a crowded field of eight candidates for their June 3 primary that includes state Sen. Leonard Lance, local mayor Martin Marks and Kate Whitman, a former congressional aide who is the daughter of former New Jersey Gov. Christine Todd Whitman.

CQ rating: Leans Republican

5) Keith Fimian, Republican, Virginia’s 11th ($742,000)

Incumbent: Thomas M. Davis III , Republican

Like several others on this list, Fimian is among the best-funded open-seat candidates in part because he began running before the incumbent made a retirement announcement. Fimian, the founder of a home inspection company, was never going to wage a primary challenge to Davis, a locally popular Republican centrist who headed the Republicans’ national House campaign committee for the 2000 and 2002 elections. But he wanted to ready a campaign organization in the event Davis did not seek re-election — a decision the congressman announced in January.

Fimian, who is unopposed in the June 10 Republican primary, has collected virtually all of his campaign funds from individual donors or in the form of personal loans he made to his own campaign. The Democrats, who are heavily targeting this partisan swing district for a takeover bid this fall, have a four-candidate primary that includes Gerry Connolly, chairman of the Fairfax County board of supervisors, and Leslie Byrne, a former member of the U.S. House (1993-95) and the Virginia Senate.

Democrats have recently made inroads in the 11th, located in the Northern Virginia suburbs of Washington, D.C.

CQ rating: No Clear Favorite

6) Erik Paulsen, Republican, Minnesota’s 3rd ($688,000)

Incumbent: Jim Ramstad , Republican

Paulsen, a state representative, is the presumed Republican nominee in a suburban Minneapolis district that Ramstad is leaving open after 18 years. Paulsen’s Democratic opponent will be Ashwin Madia, a lawyer and Marine Corps veteran of the Iraq War. Both Paulsen and Madia were recently endorsed by the party organizations in the congressional district, effectively installing them as the nominees ahead of the September primary elections.

Ramstad is a well-liked Republican moderate in this politically competitive district, and the Democrats are trying to define Paulsen as too conservative for this constituency. Republicans are portraying Madia as too liberal.

CQ rating: No Clear Favorite

7) Will Shafroth, Democrat, Colorado’s 2nd ($682,000)

Incumbent: Mark Udall , Democrat

Shafroth, who has a long career as a Colorado conservationist, is a candidate in a Aug. 12 primary election that includes Jared Polis, a wealthy businessman, and Joan Fitz-Gerald, a former president of the Colorado Senate. The 2nd District takes in left-leaning Boulder and Colorado’s ski communities, and the Demcoratic primary winner almost certainly will succeed Udall — the five-term Democratic incumbent who is the party’s presumed candidate for this year’s U.S. Senate race to succeed retiring Republican Wayne Allard .

Shafroth reported fewer total receipts ($1 million) than either Fitz-Gerald ($1.1 million) or Polis ($1.6 million) through the end of March. But he raised more from individual donors than any other candidate, and he had the most cash on hand because he’s spent a smaller share of his receipts.

CQ rating: Safe Democratic

8) Dan Maffei, Democrat, New York’s 25th ($676,000)

Incumbent: James T. Walsh , Republican

Maffei, a former congressional aide, was gunning for a rematch with Walsh after coming within 2 points of blocking the long-popular incumbent’s bid for a 10th term. But Walsh said in January that he would retire rather than seek an 11th term in and around Syracuse. Maffei’s early start for what has become a open-seat race helps explain why he is so well-funded — and his large cash reserve can be attributed in part to the fact that he’s the only Democrat running in a race that includes several contenders for the Republican nomination. The primary will be held Sept. 9.

As one of just eight districts that went Democratic for president in 2004 and Republican for the U.S. House in 2006, New York’s 25th will be one of the tougher holds nationally for the Republicans.

CQ rating: No Clear Favorite

9) Debbie Halvorson, Democrat, Illinois’ 11th ($673,000)

Incumbent: Jerry Weller , Republican

Halvorson, a state senator, was unopposed in the Feb. 5 Democratic primary for the seat from which Weller is retiring after seven terms. The district south and west of Chicago leans Republican, but not overwhelmingly, and Democratic strategists had it on their target list — even before the Republican primary winner, local mayor Tim Baldermann, withdrew from the race soon thereafter.

Under Illinois law, Republican officials in the 11th were permitted to designate a new candidate, which they did on Wednesday by choosing concrete company executive Martin Ozinga. He has a lot of catching up to do, giving his very late start and the peculiar circumstances that brought him into the race. Republicans are trying to give him a boost by linking Halvorson to Democratic Gov. Rod R. Blagojevich , who has poor approval ratings.

CQ rating: Democrat Favored

10) Steve Stivers, Republican, Ohio’s 15th ($600,000)

Incumbent: Deborah Pryce , Republican

Stivers, an Iraq War veteran, began his campaign for Pryce’s open seat months after Democratic rival Kilroy began organizing her effort. But he’s shown some early fundraising strength, and if he loses to Kilroy this November, it won’t be because he didn’t have the resources to wage an aggressive race.

Befitting a Republican nominee in a highly competitive open-seat race, Stivers has begun to rake in the contributions from political action committees aligned with Republican members of Congress and conservative groups who want to see Pryce’s seat remain in GOP hands. District voters favored Bush in the 2004 presidential race, but just barely, by 1 percentage point.

CQ rating: No Clear Favorite