Democrat John Adler narrowly defeated Republican Chris Myers in the pivotal race for New Jersey's Third Congressional District, a longtime GOP stronghold that drew national attention from both parties this year.

Adler's victory in the South Jersey district, aided by strong Democratic turnout and the retirement of 24-year Republican incumbent Rep. James Saxton, gave New Jersey Democrats an 8-5 edge in the U.S. House delegation, up from 7-6.

But Republicans held onto two other seats considered vulnerable in a Democratic landslide, as GOP candidates won in the Fifth and Seventh Districts in north and central New Jersey.

In other House races in South Jersey, incumbents prevailed: Democrat Rep. Robert Andrews in the First District and Republican Rep. Frank LoBiondo in the Second District. Republican incumbent Rep. Christopher Smith won reelection in central New Jersey's Fourth District.

Democrats maintained their control of both U.S. Senate seats, as incumbent Sen. Frank Lautenberg handily won reelection.

Adler, a Cherry Hill lawyer and state senator, won a bruising and expensive campaign over Myers, a Lockheed Martin vice president and the mayor of Medford. The seat was one of the GOP seats targeted by national Democratic leaders, who aided Adler with fund-raising, advertising and strategy.

Myers, who got a $65,000 fund-raising boost from President Bush, tried to distance himself from the unpopular president, saying in one ad, "Look, folks, George Bush is part of the problem."

Adler told 500 cheering supporters at the Mount Laurel Marriott last night that he regarded his victory "as a mandate for positive change in society."

He acknowledged his Republican predecessor, Saxton, as "someone who was very special to this region," and he said he would work with Republicans and Democrats.

"I thank all the people who voted for me, and all who didn't vote for me, because we're all Americans," Adler said.

Myers, at the Union Fire Company hall in Medford, told his disconsolate supporters, "It's a bad year to be a Republican."

He said Cherry Hill and Willingboro voted overwhelmingly for Adler, enough to overcome Myers's GOP support in Ocean County.

"I don't think it's any one issue, I just think in general folks wanted a change, and they weren't looking to the Republicans for that change."

Saxton chalked up the change in the district to the momentum Obama created at the top of the ticket.

"Obama tucked New Jersey away weeks ago, and when you have that kind of current running at the top of the ticket, it's hard for anyone. It would have been hard for me for all my 12 terms to compete in this race," Saxton said.

He said he believed the district was still fundamentally Republican, with its military bases, defense contractors and senior citizens, but that many had become disenchanted with President Bush.

Deb Miller, 37, a McCain supporter from Little Egg Harbor Township, said she split her ticket to vote for Adler because she doesn't agree with Myers on several key issues, including the environment.

"I am a registered Republican, but I don't always vote straight down the ticket," Miller said. "I'm very concerned about offshore drilling here."

Lee Myers, of Moorestown, said his support for Obama led him to vote for other Democrats down the ballot, including Adler.

"There's probably not a lot of difference at the end of the day between Adler and Myers, but I want to support Obama's ticket," he said. "There's some coattail politics there."

In the First District, Andrews easily won over Republican Dale Glading, the founder of a prison ministry based in Moorestown. Andrews won despite promising in the spring that he would not run for reelection, when he was trying unsuccessfully to unseat Lautenberg in the Senate primary.

In the Second District, LoBiondo easily warded off a challenge by Democrat David Kurkowski, a Cape May City councilman and market-research consultant. LoBiondo has held the seat since 1995.

In two other districts considered vulnerable to a Democratic tide, Republicans won:

Rep. Scott Garrett defeated Rabbi Dennis Shulman, a blind psychologist, in the Fifth District representing Warren County and parts of Bergen, Sussex and Passaic Counties.

State Sen. Leonard Lance defeated Linda Stender, a state assemblywoman, in the Seventh District in central New Jersey, which covers parts of Hunterdon, Middlesex, Somerset and Union Counties. Incumbent Republican Rep. Mike Ferguson, who narrowly defeated Stender in 2006, did not seek reelection.

Contact staff writer Paul Nussbaum at 215-854-4587 or pnussbaum@phillynews.com.

Inquirer staff writers Maya Rao, Jonathan Tamari and Jacqueline L. Urgo contributed to this article.