President Obama is supporting Rep. Steven R. Rothman, left, while former president Bill Clinton is supporting his rival for the House seat: Rep. Bill Pascrell Jr. (Charles Dharapak/AP)

A contentious New Jersey congressional primary between two Democratic House incumbents is attracting the attention of two of the most powerful Democrats in the country, President Obama and former president Bill Clinton.

The problem is that they are on opposite sides of the fight.

The contest, in northern New Jersey, between Rep. Steven R. Rothman and Rep. Bill Pascrell Jr. has exposed old wounds in the Democratic Party dating to the bitter 2008 primary contest between Obama and Hillary Rodham Clinton.

Obama is backing Rothman, while Bill Clinton is supporting Pascrell. Their reasons are simple: Rothman endorsed Obama in the 2008 primary, and Pascrell endorsed the former first lady.

Now it’s payback time.

So before flying to Minnesota on Friday, Obama held a 15-minute meeting in the Oval Office with Rothman and then took the congressman on a short walk in view of the White House press corps. Rothman later provided an analysis of the visit’s meaning even though the president said nothing publicly.

“I think it’s fair to say that he was not unmindful that appearing with me as we walked along the White House colonnade in full view of the entire White House press corps might very well make it into the New Jersey newspapers,” said Rothman, who is the only candidate in “member vs. member” primaries to win Obama’s endorsement.

Not coincidentally, Pascrell was scheduled to appear with the former president Friday night.

Obama and the Clintons appear to have fully reconciled after the 2008 primary skirmish, but their contentious history has been a consistent subtext of national Democratic politics during the past four years. The former president has appeared at Obama fundraisers, and the two will appear together at an event Monday.

Veteran Democratic operatives said that the New Jersey divide is a natural consequence of old rivalries but that it is more about loyalty rather than animosity.

“Both Clinton and Obama have been helping candidates who supported them in the past,” said veteran Democratic operative Joe Trippi. “Occasionally it has put them on opposite sides of some tough primaries, but it’s about loyalty to past supporters, not a rift between them.”

Trippi noted that Bill Clinton endorsed Colorado House Speaker Andrew Romanoff in 2010 over Sen. Michael F. Bennet, who had Obama’s support. Clinton eventually campaigned with Bennet.

This year, Clinton has backed other Democratic primary candidates in California, Maryland, Pennsylvania and Texas who endorsed his wife’s presidential bid.

Still, the clash in New Jersey comes at a time when the former president appears to be “off the reservation” with regard to the Obama campaign’s message on Mitt Romney’ s career as a private equity executive.

While the Obama campaign has been trying to portray the presumptive Republican nominee’s business career as one driven, to an exceptional degree, by greed and disregard for the little guy, Clinton described it this week as “sterling.”

“I don’t think that we ought to get into the position where we say this is bad work,” Clinton said Thursday night on CNN. “This is good work.”

New Jersey political observers said Friday that Obama’s decision to take sides in the primary carried some risks but that Obama was in Rothman’s debt. Russ Baker, a political science professor at Rutgers University and a longtime Garden State political observer, said Obama had to show his gratitude to Rothman for his early support in 2008.

“They couldn’t give Rothman a cold shoulder,” Baker said. “He needed to have some kind of ‘laying of the hands’ on Rothman.”

Whatever their motives, the two Democratic presidents have waded into a very ugly, very personal fight.

Pascrell and Rothman were both elected to Congress in 1996. Both had been mayors of towns in North Jersey; Pascrell in Patterson, Rothman in Englewood. They were Democrats from neighboring districts who came to Washington to try to turn back the Gingrich revolution and they endured, each reelected seven times. Over the years, they developed a close friendship during train rides to Washington and over dinners fueled by red wine and cigars.

But when New Jersey lost one of its 13 congressional seats after the 2010 Census, state officials redrew the congressional map and divided up their districts. Faced with the prospect of retiring, running in another district or facing off against Pascrell, Rothman chose to challenge his friend as each tried to hold on to the most friendly territory they could find.

“Bill wanted to run where he was born and raised, and I wanted to run where I was born and raised and where I actually represented for the last 16 years in Congress,” Rothman said. And because of Rothman’s decision, the pair “haven’t gone drinking since then.”

Pascrell is clearly miffed.

“With friends like that, I don’t need enemies,” he said. “He’d rather fight against his ‘friend’ Bill Pascrell. We’re supposed to be winning back the majority in the House.”

Pascrell and Rothman face each other in one of a dozen primaries across the country spawned by the redistricting and reapportionment process that has forced incumbents of the same party to campaign against each other.

Rothman said the White House support should remind New Jersey Democrats that he’s the candidate most supportive of the president’s policies.

“With regards to the perception that President Obama supports me and former president Clinton supports my opponent, I’m extremely comfortable with that,” Rothman said.

For his part, Pascrell, who eventually endorsed Obama in 2008, said in an interview that he appreciates Bill Clinton’s support, but noted: “I have a voting record that is 94 percent in support of the president’s agenda. My opponent has a 91 percent ranking.”

As the friendship dissolved, each has called the other a liar and questioned his opponent’s Democratic bona fides.

“I’m respectful of his family,” Pascrell said of Rothman, “but I have very little respect for him now because of the campaign he waged.”

Rothman said he thinks the two could eventually heal their wounds.

Staff writer Paul Kane contributed to this report.