TRENTON Fueled by a surge in spending by independent groups, the 2013 state elections were the most expensive in New Jersey history, according to a preliminary analysis released Thursday by an election watchdog.

Independent special-interest groups - which proliferated nationwide after a series of Supreme Court decisions in 2010 - spent nearly $41 million on state campaigns in the Nov. 5 elections, the New Jersey Election Law Enforcement Commission said.

That figure accounted for one-third of a record $129 million spent on the elections, up from $97 million in 2009 and $119 million in 2005, according to postelection reports filed with ELEC.

Garden State Forward, a super PAC formed by the New Jersey Education Association, spent $13.9 million on the gubernatorial and legislative races, the most of any outside group.

The Fund for Jobs, Growth and Security, a Washington-based super PAC, spent about $8 million to help elect Democrats in legislative races. The group also spent $680,000 to help secure approval of a ballot referendum that increased the state's minimum wage.

It poured $822,000 into races in the Second Legislative District, where Northfield Mayor Vince Mazzeo, a Democrat, eked out a 39-vote victory over Republican incumbent John Amodeo after a recount completed this week.

George E. Norcross III, a South Jersey Democratic power broker, helped raise money for the fund, according to a Democratic source. Norcross, who is also a part-owner of The Inquirer, declined to comment Thursday on his involvement with the fund.

The top Republican-allied outside group, Committee for Our Children's Future, spent $7.8 million in the gubernatorial primary in support of Gov. Christie, who easily won reelection over State Sen. Barbara Buono.

Christie outspent Buono $13.1 million to $3 million, according to ELEC.

The flood of money did not change the power structure in Trenton. Democrats maintained the same majority they held in each house of the Legislature heading into the elections, and Republicans retained the governorship.

Of the $10.5 million in independent spending for which ELEC was able to identify party affiliation, $8.8 million, or 84 percent, of the money supported Democrats.

Final campaign-finance numbers will be made available in January.

aseidman@phillynews.com

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@AndrewSeidman

Inquirer staff writer Maddie Hanna contributed to this article.