NEWARK, N.J. - In preparation for what was expected to be a fierce primary campaign for the Democratic nomination for governor, two independent political groups spent more than a year raising millions of dollars to back their favored prospective candidates.

The so-called super PACs did not anticipate that Jersey City Mayor Steve Fulop and Senate President Stephen Sweeney, once considered front-runners for the nomination, would drop out before the race really got started.

Now the pro-Fulop and pro-Sweeney political action committees must decide how to spend their money - and how to attract donors who thought they were supporting a different cause.

The Fulop-aligned Coalition for Progress, founded in August 2015, reported having $3.2 million in cash as of June 30. New Jerseyans for a Better Tomorrow, the pro-Sweeney group, had $1.2 million, according to campaign-finance records.

They groups have likely raised more money, since those reports do not account for third-quarter fund-raising.

Fulop and Sweeney, of Gloucester County, both said they would seek reelection to their current offices and endorsed Democrat Phil Murphy, a former Goldman Sachs executive and ambassador to Germany, for governor.

Sweeney's "decision to return to the state Senate is critical for the future of this state, and we will continue to support his endeavors," said Sean Kennedy, chair of New Jerseyans for a Better Tomorrow and a former aide to the Senate president.

"We know in his immensely capable hands, the Legislature will push for what's best for New Jersey, and we will undo the damage that Chris Christie's irresponsible administration has done to our state."

Kennedy added that Sweeney "would have made a fantastic governor" and that "hundreds of donors and supporters clearly shared that belief."

Asked whether any donors had sought refunds since Sweeney's announcement last week, Kennedy said they had not.

Bari Mattes, president of Coalition for Progress, did not respond to an email seeking comment about the PAC's spending plans, including whether it would support Fulop's mayoral reelection campaign or return contributions to donors.

The PAC will have plenty of options, such as boosting Murphy's bid with TV ads or intervening in state and local races with ads and mailers. Indeed, in 2015, Kennedy's PAC donated $25,000 to another outside group that helped Democrats in legislative races.

Super PACs can raise unlimited sums of money for elections but cannot coordinate with the campaigns they support.

"A PAC has no fiduciary duty to its donors and is free to spend on behalf of other candidates as long as the super PAC has not coordinated with that candidate," said Kenneth A. Gross, a partner with Skadden, Arps, Slate, Meagher & Flom LLP in Washington and former associate general counsel with the Federal Election Commission.

"There is no duty of the super PAC to return any money, although it may do so voluntarily," he said.

Neither PAC said in its organizational statement that it would support a specific candidate.

The pro-Fulop Coalition for Progress' August 2015 statement of organization, filed with the Federal Election Commission, said: "This committee supports/opposes more than one federal candidate and is NOT a separate segregated fund or a party committee."

New Jerseyans for a Better Tomorrow, which registered with the state Election Law Enforcement Commission, said in May 2015 that it would support "candidates for elected office in the state of New Jersey through independent activity."

Sweeney, a former Gloucester County freeholder director who has represented the Third Legislative District in the state Senate since 2002, has never lost an election.

He may well have a target on his back in 2017, especially after he refused last summer to hold a vote on a proposed constitutional amendment that would require the state to make greater contributions to the pension system for public workers.

Sweeney accused the state's largest teachers' union of attempting to bribe lawmakers with campaign contributions in exchange for their vote.

He also supported bipartisan legislation, expected to be signed into law by Christie, to more than double the state's gasoline tax, which could invite a strong general election challenge from a Republican. The legislation also includes various tax cuts.

Senate Republicans targeted Sweeney's seat in 2013, but he won by a commanding 9 percentage points in his somewhat rural district. Since then, as he prepared for a gubernatorial run, he has moved to the left on issues like gun control, supporting a stricter limit on magazine capacity.

Should Sweeney win reelection next year, North Jersey power brokers fatigued by South Jersey's influence in Trenton could seek to oust him as Senate president, a position he has held since 2010.

All that makes the super PAC an important asset for Sweeney - even if it doesn't land him in the governor's mansion.

856-779-3846 @AndrewSeidman