Introduction

New Jersey Senate candidate Newark Mayor Cory Booker addresses a gathering of supporters at a June 18 event in Deptford Township, N.J. Mel Evans/AP

With the primary just weeks away, new super PACs are popping up to boost — or bash — Newark Mayor Cory Booker’s candidacy in New Jersey’s crowded U.S. Senate special election.

A recently formed super PAC called the Mobilization Project made its foray into the race with a canvassing operation costing nearly $74,000 in support of Booker’s bid, Federal Election Commission filings today show.

That follows an effort from another new super PAC, American Commitment Action Fund, which announced a $100,000 online advertising campaign against Booker this week. FEC records don’t indicate the money has yet been spent.

(Update, 9:17 p.m.: A filing with the FEC on Wednesday night indicates American Commitment Action Fund spent an initial $13,030 early this week on ads opposing Booker’s candidacy.)

American Commitment Action Fund is the super PAC arm of American Commitment, a conservative 501(c)(4) nonprofit organization that spent more than $1.8 million on the 2012 elections, according to federal records.

Less is known about the Mobilization Project, which filed its organizational paperwork with the FEC on July 15. The group does not have a website, and its treasurer, Gary Gruver, could not be reached for comment Wednesday.

The super PAC uses the former P.O. Box address of the September Fund, a liberal 527 organization founded by Harold Ickes, a political operative with close ties to Bill and Hillary Clinton.

The group, which also lists Gruver its treasurer, has not been active in recent elections, but spent nearly $5 million during the 2006 midterms, according to the Center for Responsive Politics.

Since the Mobilization Project and American Commitment Action Fund officially launched after the FEC’s mid-year filing deadline, the groups will not be required to disclose their donors until Aug. 1, according to FEC regulations.

Garden State voters will head to the polls on Aug. 13 for the primary election, while the general election is slated for Oct. 16. New Jersey Gov. Chris Christie called the special election shortly after Sen. Frank Lautenberg, D-N.J., died in June.

Aside from Booker — the favorite to win the seat — U.S. Reps. Frank Pallone, D-N.J., and Rush Holt, D-N.J., and Democratic Assembly Speaker Sheila Oliver have also entered the race.

On the Republican side, former Bogota, N.J., Mayor Steve Lonegan and physician Alieta Eck are running.

The Pallone campaign has repeatedly called on their fellow Democrats in the race to agree to a pledge dissuading outside groups from participating in the primary, similar to one introduced in recent Massachusetts Senate elections. But none of the candidates have signed on.

“There’s no need to have outside money in this race. Shouldn’t we all stand up and say ‘no’?” Pallone spokesman Jeff Carroll said. “Let’s have a clean race and set an example.”

Holt spokesman Thomas Seay said the campaign has not accepted Pallone’s call to limit outside group activity because “as written, the text of the pledge is nonsensical.”

However, he wrote in an e-mail that “it’s unfortunate outside interest groups are intervening in such an opaque and unaccountable way,” and that Holt would “work to overturn Citizens United and fight for public disclosure of all major political donors” if elected to the Senate.

Booker’s campaign could not be reached for comment.

But in a fundraising email to supporters Wednesday evening, Booker lamented that “we found out yesterday that a tea party super PAC is attacking us.”

Then, in making a pitch for money, he said: “We only have a few more hours to prove to everyone in New Jersey that we’re stronger than this challenge … a few more hours to prove that we will not be deterred by forces that want to distort my record and take our state and country backwards.”

The early flow of outside money into New Jersey is unlikely to subside. The San Francisco-based group Pac Plus pledged last month to spend $2 million in support of Booker’s candidacy, but so far, it has yet to report any expenditures.

New Jersey saw relatively little spending from outside groups — about $1.5 million — during the state’s 2012 U.S. Senate contest between Sen. Robert Menendez, D-N.J., and Republican nominee Joe Kyrillos.

Ben Wieder contributed to this report.