As it appears increasingly inevitable that Sen. Jon Corzine (D-N.J.) will be elected governor in November, the public and private maneuvering to succeed him has recently intensified within the Garden State’s Congressional delegation.

The behind-the-scenes primary to win Corzine’s appointment to the seat he now holds reached a new level Friday, as Rep. Bob Menendez (D-N.J.) raked in an estimated $2.5 million at a major fundraiser in the state. The event was widely seen as confirmation that Menendez is running for the position.

Menendez, chairman of the House Democratic Caucus, and fellow Democratic Rep. Frank Pallone appear to be the leading Members seeking Corzine’s blessing, with both working to shore up key support throughout New Jersey. Rep. Rob Andrews (D) is also seen as a possible candidate.

If elected in November, Corzine will tap his successor to complete his current Senate term, which expires in January 2007. The new Senator would then be expected to compete for a full term in a June primary and the 2006 general election.

While the two lawmakers share the same goal, they are employing drastically different strategies to enhance their prospects — Pallone leading a very public campaign to succeed Corzine and Menendez largely keeping his powder dry.

But on Friday, Menendez indirectly answered many of the questions about his interest at a 1,400-person fundraiser at the New Jersey Meadowlands that swelled his campaign account to more than $4 million. And his spokesman took it a step further, saying in the strongest words yet that Menendez will run if a seat is available.

“If there is a vacancy, he plans to pursue it,” Matt Miller said.

Sources said they don’t expect Menendez to say anything beyond that for now, sticking with his strategy of trying to position himself financially and politically as to appear to be the strongest candidate for the appointment. With the latest fundraiser, the seven-term Democrat added to the $1.6 million he reported in the bank at the end of last year.

“The weirdest thing is there is this intense campaign for a seat that doesn’t even exist at this point,” noted a Menendez strategist, who said Menendez is “clearly interested if the seat opens up” but is keeping the goal of getting Corzine elected at the forefront.

The strategist said that while Menendez’s interest in the post has been consistent since then-Gov. Jim McGreevey (D) announced his resignation in August, the political stakes of the appointment are hitting a new level.

“The fundraiser is an annual event, but he probably raised 50 percent more than he did previously,” the strategist said. “Obviously, the interest [by others in Menendez] has been ratcheted up now that he may well be the Democratic Senate candidate.”

Menendez has put in place a team of campaign operatives in New Jersey — including a message team and pollsters — and tapped into a national network. He recently hired a new press secretary, Miller, who comes from Sen. John Kerry’s (D-Mass.) presidential campaign, and named a seasoned campaign aide as his personal chief of staff, Ivan Zapien.

Many of Menendez’s current ring of political advisers have been with him for several years but also have worked to elect Corzine and McGreevey.

In his inner circle are the firm Message and Media and veteran Democratic pollster Joel Benenson. Menendez has also tapped Kiki McLean of the Dewey Square Group in Washington, D.C., who advised then-Vice President Al Gore on his White House bid in 2000.

Several Menendez strategists, speaking on the condition of anonymity, said the Garden State Congressman is trying to show Corzine, local Democratic leaders and voters and national party officials that he is the best candidate to hold the post. If appointed, Menendez is likely to face a tough general election campaign, with state Sen. Tom Kean Jr. the Republicans’ favored contender.

“If you look at the people who have been mentioned as potential candidates for the Senate in New Jersey, none has demonstrated the fundraising ability that Bob Menendez has,” said another Menendez political strategist.

This operative said Menendez’s current game plan is to continue to work to elect Corzine governor while building a financial and political base. At the “appropriate time,” the adviser said, Menendez will become more public about his candidacy by laying out his record and vision for the state.

While Menendez has largely been operating under the radar and keeping his interest in the contest private, Pallone has been aggressively traveling the state and openly stumping for the Senate appointment.

He held a campaign “kickoff” event last month, opened a new campaign account and launched a Senate Web site.

Like Menendez, he too is trying to score points by helping Corzine.

“He is working hard for Sen. Corzine and also dovetailing that with his own ambitions,” a Pallone strategist said.

Although privately acknowledging it may be tough to match Menendez’s fundraising prowess, Pallone allies argue that he would be the Democrat best positioned to win a competitive general election. They say that no Republican can win statewide without taking Monmouth and Ocean counties, portions of which he either currently or has previously represented.

“We really have the linchpin in electability in the general election,” a Pallone strategist said. “That’s what really sells Frank.”

Pallone launched a Senate campaign Web site in February and has signed media firm McMahon, Squier and Associates to work on a possible statewide campaign.

Pallone, who opened a Senate campaign account earlier this year, estimates that he raised about $400,000 in the first quarter of the year.

His Senate account is expected to show a balance of $250,000 to $300,000 when Federal Election Commission reports are filed later this week. Most of that total was raised at Pallone’s Senate campaign kickoff event last month. He also has $1 million in his House re-election account that he can use toward a Senate bid.

While there has been some speculation that Corzine might opt to appoint a placeholder as his successor — someone who would not seek a full term in November 2006, creating a fair fight in the June primary — there is increasing doubt within Democratic circles that that scenario will unfold.

One state Democratic source said that Corzine, who averted a bloody primary with current acting Gov. Richard Codey (D) thanks to the early support of key party leaders, owes too much to too many people not to appoint a true successor.

“Putting a placeholder there is problematic on two levels,” said the source. “One, because I think he’d be disappointing too many people. Two, there’s a general election in 11 months.”

Also complicating the placeholder idea is the fact that Kean has already announced the formation of a 2006 Senate exploratory committee. Kean, a moderate like his father, former Gov. Tom Kean (R), is considered perhaps the Republicans’ most formidable general election candidate.

Kean’s early interest in the race has increased the pressure on Corzine to appoint the strongest possible Democratic nominee, Democratic sources say, and likewise shifted the burden to prospective appointees to prove they fit that bill.

“I think with Tom Kean Jr. in there, his appointment becomes even more critical,” the source said. “Because you need somebody there who can demonstrate that they can win a general election. I think the burden is now on Pallone, Menendez and Andrews … [to prove] who would be the best general election candidate.”

Several political observers say that while he has not done anything overt to promote himself in recent weeks, Andrews cannot be counted out. His endorsement of Corzine in the governor’s election several weeks ago effectively put Codey out of the race.

Andrews, the only one of the potential candidates with a political base in the southern half of the state, said recently that he is “very interested and preparing to run” by raising money and reaching out to local political officials and interest groups.

Andrews, however, said his first priority is getting Corzine elected governor.

“I am confident he’s going to win, but we’ve got a lot to do before that,” he said.