There’s an interesting theory about New Jersey voters that appears to be supported by a recent poll concerning the re-election chances of Sen. Frank Lautenberg (D).

You might even call it the New Jersey discount.

A Monmouth University/Gannett New Jersey poll of 698 registered New Jersey voters conducted earlier this month found that 58 percent of respondents felt it was time for someone else to fill Lautenberg’s seat in the Senate.

And yet, when Lautenberg, who turned 84 on Wednesday, was tested in a hypothetical matchup against two announced Republican candidates, he trounced both.

For those who may think this contradictory polling result is just a factor of this particular race, it might be helpful to recall Sen. Bob Menendez’s (D) 2006 race for a full term, when a similar polling quandary played out.

In that matchup against Republican Tom Kean Jr., much was made of Menendez’s low polling numbers in the months before Election Day. In July 2006, one Quinnipiac University poll placed Menendez’s job approval numbers in the low 30s and another poll in September found his favorable/unfavorable numbers separated by just a few points.

But Menendez went on to win his Senate race by 9 points in November.

So what’s the matter with New Jersey? And is Lautenberg in any political danger at all?

“On a generic side, New Jersey [polling] numbers depress compared with the rest of the nation,” explained one New Jersey Democratic consultant who is working for Lautenberg’s campaign. “It’s a historical gap and it works for everybody so it’s not unique to the Senator.”

The consultant explained that most candidates in New Jersey have higher unfavorable ratings than comparable candidates in other states for a host of reasons, not the least of which is a difficult and expensive media market dynamic where candidates usually don’t go on the air until the home stretch of a campaign.

The consultant added that there’s also “the cynicism of New Jersey voters — which is well-earned, I might add — so in historical context [Lautenberg’s numbers in the Monmouth poll] are decent and people with these numbers and worse have gone on to comfortable victories.”

Patrick Murray, director of the Monmouth University Polling Institute, agreed that while Lautenberg’s 43 percent to 28 percent approval/disapproval rating might be considered a possible sign of weakness in another state, Lautenberg’s continued strength is evident when voters are forced to pick one candidate over the other. In cases like these, Democrats almost always have the edge.

“The deal in New Jersey is that Democrats can afford to put up a flawed candidate and the Republicans can’t,” Murray said. “That’s really the bottom line, because we have become a blue state and I think that’s what you saw with the polling in the 2006 race. It indicated that it was tough for people to say they’d really endorse Menendez as a candidate on his own, but when it came down to making a choice in the voting booth, they had to go with the Democrat.”

One Capitol Hill Republican even acknowledged the baseline Democratic advantage in the Garden State.

“New Jersey is different than most other possibly purple states in that the Democratic base tends to be more active,” the Republican said. “But I don’t think voters know anything about the Republicans running in this state yet, and the numbers could change once people start to get to know them.”

Those Republicans include state Assemblyman Joe Pennacchio, wealthy real estate developer Anne Evans Estabrook and college professor and libertarian activist Murray Sabrin.

Earlier this week, Sabrin earned the endorsement of long-shot GOP presidential hopeful Rep. Ron Paul (Texas). Meanwhile, Estabrook, who has lent her campaign more than $1.5 million, spent last week touting her campaign contributions from a few of the Senate’s top Republicans last week. She made her announcement on the same day that Pennacchio officially launched his campaign for the GOP nomination.

The Monmouth poll did not include a head-to-head matchup against Murray but showed Lautenberg leading Pennacchio 40 percent to 25 percent and Lautenberg ahead of Estabrook 38 percent to 24 percent.

It’s those numbers — along with another statistic that showed Lautenberg’s age was less of a negative factor in voters’ minds than previous polls have suggested — that Lautenberg’s supporters say are the takeaway numbers from the most recent poll.

Even if the numbers aren’t sterling, Lautenberg already has won four Senate elections, and there’s little evidence that voters’ confidence in him has eroded significantly. That should dampen any distant hopes of ambitious Garden State House Members that the Senator may choose, at the last minute, to retire.

“This poll makes clear that voters believe Sen. Lautenberg is a strong voice for New Jersey and shows a commanding lead over any of his potential Republican opponents — and those are the numbers that matter,” said Lautenberg’s campaign manager, Brendan Gill.

“The people of New Jersey approve of the job the Senator is doing because he is standing strong for the state in the U.S. Senate and making a real difference in people’s lives.”