LOS ANGELES (AP) — California’s redrawn political map opened the door this year to the priciest and hardest-fought House races in decades, forcing incumbents to fight for their jobs, ousting the state’s longest-serving congressman and leaving several contests undecided Wednesday.

Even as most veterans of California’s largest-in-the-nation congressional delegation prepared to return to Washington, others, such as long-time GOP moderate Rep. Mary Bono Mack, dug in to defend seats as Democrats pulled ahead in a handful of retooled, suburban districts.

Returns trickling back Wednesday showed Democrats maintained a slight edge in races in the Sacramento, Palm Springs and San Diego areas, with only absentee ballots left to count.

“Because of redistricting, candidates were facing substantially new constituencies this year,” said Jack Pitney, a political scientist at Claremont McKenna College. “There were some survivors but overall the big losers are the Republicans, who were also dealing with some serious headwinds from the top of the ticket.”

Rep. Pete Stark, who had represented his San Francisco Bay area district since the end of the Vietnam War, was one of two Democrat casualties unseated by members of their own party in House races reshaped by an independent redistricting committee.

Stark, 80, lost to an upstart challenger nearly 50 years his junior, Democratic Dublin City Councilman Eric Swalwell.

He was undone in part due to a new primary system that sends the top two vote-getters to the November ballot, forcing runoffs in some cases between party brethren.

That also ended the House career of 30-year Democratic Rep. Howard Berman in the San Fernando Valley of Los Angeles, where Democratic Rep. Brad Sherman netted the single seat left after the district’s boundaries were redrawn.

Their nasty battle even got physical when Sherman roughly grabbed the smaller, older Berman by the shoulder during a debate, pulled him toward his chest and hollered, “You want to get into this?”

State congressional races drew intense interest nationally, after gerrymandered strongholds were transformed into free-for-alls flooded with campaign cash from groups as varied as Planned Parenthood and Americans for Tax Reform, headed by low-tax crusader Grover Norquist.

Super PACs and other outside groups flooded California’s House races with more money than any other state under new rules allowing unrestricted outside political spending. By Tuesday, spending had reached nearly $54 million, according to the Center for Responsive Politics.

Investing in California’s congressional races helped Democrats reduce the GOP majority in the House and bring in new members who represent the state’s increasing diversity, said Andy Stone, spokesman for the House Majority Pac, the leading Democratic super PAC in this year’s races.

Three House races remained hotly contested Wednesday afternoon as returns showed Democratic challengers maintaining a razor-thin edge.

In the suburbs south of Sacramento, GOP Rep. Dan Lungren was struggling to fend off Democratic physician Ami Bera, who held a slight advantage with only absentee ballots left to count. His GOP colleagues Reps. Brian Bilbray of San Diego and Bono Mack of Palm Springs also were trailing, returns showed.

In the rural San Joaquin Valley, freshman Republican Rep. Jeff Denham staved off his Democratic challenger, former astronaut Jose Hernandez. The district, split evenly between Democrats and Republicans, attracted more than $8 million from political action committees and other outside groups.

Democratic Reps. Jerry McNerney in Stockton and Lois Capps in Santa Barbara kept their seats, defeating well-funded GOP opponents.

Democratic Rep. John Garamendi, who has held state and federal offices for nearly four decades, trounced Kim Vann, a 37-year-old pro-abortion rights Colusa County supervisor who national Republicans had considered a top hope for picking up a seat.

One exception among the incumbents was Stark. The lawmaker had coasted to re-election in his liberal Northern California enclave since he was elected in 1972, until more moderate suburbs were included in his district. Swalwell’s pledge for fresh ideas and bipartisan cooperation played better with voters.

“I went to Washington by running against an unpopular war and for women’s rights, opportunity for children and dignity for seniors,” said Stark, who congratulated Swalwell on Wednesday. “I leave knowing that the landscape has changed, but the needs of my constituents remain.”

The state’s delegation has been composed of 33 Democrats and 19 Republicans, with the seat of former Democratic Rep. Dennis Cardoza up for grabs next year after he resigned in August when the fall ballot was already set.

Democrat Mark Takano of Riverside, a high school teacher and former trustee of the Riverside Community College District, won a seat in the newly redrawn 41st District, once a GOP stronghold held by Rep. Jerry Lewis. Democratic state Assemblywoman Julia Brownley snapped up another seat along the Ventura County coastline that had been held by Republican Rep. Elton Gallegly, who retired.

Districts south and west of Los Angeles were some of the hottest battlegrounds, where Bono Mack sought to fend off Harvard-educated physician Raul Ruiz, an effective Democratic fundraiser adept at mobilizing the district’s growing swath of Hispanic voters.

San Diego’s 52nd district, where Bilbray is trying to fend off Democratic challenger Scott Peters, remained a tossup Wednesday afternoon.

As of Tuesday, outside groups had spent nearly $8.3 million on the race, making it the nation’s sixth-most expensive in terms of outside spending. By comparison, the campaigns together had spent $4.1 million through Sept. 30, the most recent figures available.