Now: Safe Republican

Was: Likely Republican

Dreier’s 53 percent vote share in 2008 was the lowest in any of his 14 re-election campaigns. Democratic challenger Russ Warner — the owner of a magazine distribution company — is seeking a rematch after losing by 12 percentage points last time, suggesting that Dreier potentially could be in for a competitive race.

But Dreier, who is rounding out a full three decades in Congress, has the advantages of incumbency, including seniority that gives him clout as the ranking Republican (and former chairman) of the powerful Rules Committee. Given the shift in political atmosphere since the 2008 election, and more promising prospects elsewhere in the state, Democrats are not making this seat a top priority at the moment. — Emily Cadei

California’s 48th District (Southern Orange County — Irvine, Newport Beach)

Incumbent: John Campbell , R

Now: Safe Republican

Was: Likely Republican

The 48th District, located in the longtime Republican stronghold of Orange County south of Los Angeles, got Democrats’ attention when district voters gave Democrat Barack Obama a 1 percentage-point edge in the 2008 presidential race. This was just four years after President George W. Bush enjoyed an 18-point advantage at the top of the Republican ticket.

But Campbell still won by a double-digit percentage in 2008. And despite getting an early start on fundraising, 2010 Democratic challenger Beth Krom — a councilwoman in Irvine, the district’s largest city — has raised just more than $200,000 through the third quarter, a fraction of what she’d need to be competitive in a district located in the expensive Los Angeles media market. — Emily Cadei

Colorado’s 4th District (North and east — Fort Collins; Greeley)

Incumbent: Betsy Markey , D

Now: Tossup

Was: Leans Democratic

Markey, a businesswoman and former Senate aide to Colorado Democrat Ken Salazar , scored an impressive victory over three-term conservative incumbent Marilyn Musgrave in 2008. But the outcome ran counter to the usually Republican leanings of voters in her sprawling district.

Voters in the 4th, while electing Markey, narrowly favored Republican John McCain over Obama for president in 2008. As recently as 2004, President Bush powered up to a 17-point margin as the Republican nominee.

With Republican strategists placing this race high on their 2010 target list, and a solid and experienced front-runner in the field for their nomination, Markey’s hopes for a second term appear up for grabs.

The field of Republican opponents, which started taking form early, is headed by Gardner, the minority whip of the Colorado House. With $395,000 raised and $273,000 in cash on hand as of the end of September, Gardner is one of the better-funded House challengers in the nation.

Tom Lucero, an elected member of the University of Colorado’s Board of Regents, also is seeking the Republican nomination but has raised little money.

But Markey looks prepared for the fight. She raised $951,000 in the first nine months of this year, one of the highest totals for a first-term member. She also broke with House Democratic leaders in April by voting against the party-backed budget plan for the next fiscal year. — Greg Giroux

Hawaii’s 1st District (Oahu — Honolulu, Waipahu, Pearl City)

Incumbent: Neil Abercrombie , D (retiring to run for governor)

Now: Likely Democratic

Was: Safe Democratic

Republicans’ hopes for a big upset win — in a Honolulu-based district that rarely elects Republicans — hinge on the possibility of a divisive Democratic primary and the successful recruitment of a strong GOP candidate in Honolulu City Councilman Charles Djou.

Ed Case, a Democrat who formerly represented the neighboring 2nd District, announced last March that he would run for the seat left open by longtime incumbent Abercrombie. But Case, who shortened his previous House tenure by staging an unsuccessful 2006 primary challenge to Sen. Daniel K. Akaka , only raised $169,000 through Sept. 30 for his 2010 1st District bid.

His top primary opponent is state Senate President Colleen Hanabusa, who announced her candidacy in October. Hanabusa, who twice sought the 2nd District seat, is backed by the Democratic feminist powerhouse EMILY’s List and will likely be a formidable candidate. And with a mid-September primary, party officials have to worry about a divisive Democratic contest that would leave the survivor little time to recover.

What’s more, Republicans have their best candidate in a decade running for this seat. Djou has been fundraising for this race since early 2008, when it was correctly rumored that Abercrombie would leave his House seat open to run for governor. National Republicans already have taken note of Djou and aired advertisements in the heavily Democratic district. — Shira Toeplitz

New Mexico’s 2nd District (South — Las Cruces, Roswell, Little Texas)

Incumbent: Harry Teague , D

Now: Tossup

Was: Leans Democratic

What little edge Teague had, as a Democratic freshman in a Republican-leaning district, fled when his Republican predecessor — Steve Pearce, the state’s unsuccessful 2008 Senate nominee — announced he would run in 2010 to try to reclaim the House seat he’d held for three terms.

Pearce’s $500,000 fundraising tally in the year’s third quarter just underscores what a slugfest the 2nd District race is shaping up to be. Teague is not short of cash himself as he prepares to play defense, as he raised $875,000 through Sept. 30 and led Pearce in cash-on-hand by $757,000 to $460,000. And the campaign committees of both major parties will play heavily in this tossup race.

Pearce won easy House victories with 59 percent of the vote in 2006 and 60 percent in 2004. But New Mexico as a whole shifted to the Democrats in the 2008 cycle, and Republican presidential nominee McCain (from neighboring Arizona) hung on to edge Obama for president by just 1 point in the traditionally conservative district. Teague is working hard to prove that he is that rare breed of conservative-style Democrat who fits his Republican-leaning district, but the GOP is not going to make it easy. — Emily Cadei