Jersey City Mayor Steve Fulop, once considered a favorite for the Democratic gubernatorial nomination in 2017, announced Wednesday that he would not run, jolting a race that has been underway at least since Gov. Christie won reelection in 2013.

Fulop, a former banker and Marine Corps veteran who was elected mayor in May 2013, endorsed Phil Murphy, a former Goldman Sachs executive who served as President Obama's ambassador to Germany from 2009 to 2013.

Fulop said he would seek reelection as mayor next year and praised Murphy for sharing his "progressive values."

"I don't see any winners ultimately in a very, very bloody primary," Fulop said on the steps of City Hall as Murphy stood by him. "The hope today is to ultimately unite people in a common cause."

Many New Jersey political observers said they were shocked by the news, given that Fulop had for years been aggressively courting support for a gubernatorial campaign.

"I've read on the internet all sorts of theories, none of which are true," the mayor told reporters. "I've read about my health, I've read about legal issues, I've read about Bridgegate, my wife. None of them are true. . . . I think this will ultimately be a good thing for Jersey City and a good thing for New Jersey. Cut and dry at that."

Other possible contenders for the Democratic nomination include Senate President Stephen Sweeney of Gloucester County, Sen. Raymond J. Lesniak of Union County, and Assemblyman John S. Wisniewski of Middlesex County. The primary is scheduled for June.

A super PAC founded by a fund-raiser for U.S. Sen. Cory A. Booker began raising money in the summer of 2015 for an expected Fulop campaign. The political action committee had $3.2 million in the bank as of July, according to filings with the Federal Election Commission.

Just last month, Fulop hired Michael Soliman, a strategist for Booker's 2014 Senate campaign and longtime statewide director for U.S. Sen. Bob Menendez.

Fulop, 39, is also close with former Gov. Jim McGreevey. The mayor has waded into statewide debates, such as a proposed constitutional amendment to expand casino gaming to North Jersey and Atlantic City's financial future.

Most pointedly, he picked a public fight with George E. Norcross III - the South Jersey power broker and hospital and insurance executive - over legislation proposed in Trenton that would have authorized a state takeover of Atlantic City.

"Why is an insurance broker, a nonelected official, who has made tens of millions of dollars on the backs of public taxpayers, actively involved in drafting Atlantic City's takeover bill and then lobbying for it all over New Jersey?" Fulop said in a statement in May.

Norcross responded in part that Fulop was "making a fool" of himself, adding that the mayor had traveled to his office in South Jersey and "begged for my support for governor."

Norcross, who is Sweeney's chief political benefactor, said he "respectfully declined" Fulop's entreaty.

"I think part of it was that Fulop realized it wasn't going to be him vs. Sweeney," but that Murphy would be a "force to contend with," said Patrick Murray, a political analyst at Monmouth University.

Fulop and Murphy were competing for the support of the same voters, Murray said, and over the last couple of months, Murphy had worked to win over local power brokers.

Federal prosecutors have listed Fulop as a potential witness in the trial of two former Christie allies, Bill Baroni and Bridget Anne Kelly.

The two are charged with misusing the resources of the Port Authority of New York and New Jersey to close lanes at the George Washington Bridge in September 2013 as a means of punishing a local mayor who had refused to endorse the governor's reelection.

Fulop, too, was a target of political retaliation, according to prosecutors and evidence introduced at trial.

The mayor may also draw scrutiny, however. In 2012, he worked for a Port Authority tenant called Foreign Automotive Preparation Service (FAPS).

The company was behind on rent, and the Port Authority warned the tenant in May 2012 it might soon be in violation of its lease. By November of that year, the Port Authority had resolved its dispute with FAPS and entered into a supplemental lease with the company.

David Wildstein, a former Port Authority official who has pleaded guilty in the bridge case and is the government's star witness, said the only reason the agency even made a deal with FAPS was because Fulop "was viewed as somebody who might possibly endorse Gov. Christie's campaign for reelection."

"Good meeting with Fulop today, very open about his intent to endorse - although clearly that's what I wanted to hear from him," Wildstein wrote in a Nov. 28, 2012, email to Bill Stepien, a top Christie aide who would run the governor's reelection campaign.

"Good to hear," Stepien responded, according to emails introduced into evidence. "I give him less of a chance than most of our other targets. . . . Quite the snake. We'll see. You can't say we haven't tried!"

But when the Christie campaign suspected Fulop was not going to endorse the governor, Wildstein canceled a meeting with FAPS, according to his testimony.

While Sweeney had aimed to benefit from Fulop and Murphy splitting votes in North Jersey, and Lesniak and Wisniewski potentially serving as spoilers in the central part of the state, "I think Murphy's the favorite now, and this looks like this is going to be a north-south battle," Murray said.

Two-thirds of Democratic votes are in the northern part of the state, he said.

To be sure, many key northern counties, such as Essex, are divided over which Democrat to support.

Murphy holds a financial edge; he personally lent $10 million to his campaign when he announced his candidacy in May.

State law bars Christie from a third consecutive term. Possible Republican candidates include Lt. Gov. Kim Guadagno, Assemblyman Jack Ciattarelli of Somerset County, and Assembly Minority Leader Jon Bramnick of Union County.

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@AndrewSeidman