Democrats and the White House defended attacks on Mitt Romney’s record at Bain Capital on Tuesday, calling them “fair game” and dismissing party infighting over the issue.

Senior administration officials said President Barack Obama’s campaign will continue to attack Romney’s record at the private equity company as well as his record as governor of Massachusetts as part of a larger narrative aimed at middle-class voters.

And several Senate Democrats echoed the attacks Tuesday, charging that the style of capitalism espoused by Romney helped investors at the expense of workers for decades.

“His business was to get rid of workers,” Sen. Frank Lautenberg said.

The New Jersey Democrat also took Newark Mayor Cory Booker (D) to task for calling the attacks “nauseating” on NBC’s “Meet the Press.” Those comments prompted Republicans to gleefully launch the “I Stand With Cory” campaign, much to Booker’s and the Obama campaign’s chagrin.

Lautenberg said Booker, whom some expect to run for Lautenberg’s seat in 2014, had hurt the president.

“It’s a terrible blow, in my view, for President Obama,” he said. He likened the remark to “sabotage” and said Booker needs to do more to rectify his mistake.

Booker has tried several times since Sunday to walk back the remarks. On “The Rachel Maddow Show” on Monday night, he expressed anger at Republicans who have turned his statement into campaign fodder.

As for a possible primary run against Booker in 2014, Lautenberg said “he’s welcome to do it” but that his remarks did him great damage.

“Now we have a different record,” said a smiling Lautenberg, who is considering seeking another term.

He also accused Booker of not spending enough time in Newark.

“Newark needs hands-on kind of leadership, and it’s not getting the attention,” he said. Booker’s “out of town a lot” giving speeches.

Lautenberg noted his own role co-founding Automatic Data Processing Inc., which has more than 50,000 employees: “I spent my time in business creating jobs. Romney spent his time eliminating them.”

Sen. Jeff Merkley said Romney’s Bain experience shows he doesn’t have the experience needed to help the middle class.

“It’s certainly relevant,” the Oregon Democrat said. Merkley said that productivity gains have been flowing to investors and the wealthy instead of workers since 1974. The reason is “the type of management Romney represents,” he said.

The attacks, however, have made some Democrats queasy — not just Booker. Former Pennsylvania Gov. Ed Rendell told BuzzFeed that the Obama campaign ads were “very disappointing.” The campaign has produced a series of ads in which workers who lost their jobs after Bain took over their companies blame Romney for their plights.

Sen. Mark Warner was circumspect in an appearance on MSNBC’s “The Daily Rundown,” calling Romney’s Bain experience a “valid topic of debate” even as he defended the company as “very successful.” The Virginia Democrat, who made millions as an investor, said he learned in making the transition to government that it requires a “different skill set.”

Republicans, meanwhile, were only too happy to talk about Bain and Booker. “The president can’t run on his record,” Sen. John McCain (R-Ariz.) said. “That’s what it’s all about.”

Senate Minority Leader Mitch McConnell made a broader attack.

“The whole notion of earned success and of capitalism seems to be under attack by this administration across the board — not just in the campaign, but through the actions of the government itself,” the Kentucky Republican said. “I think the view of this administration is if you’re making a profit you must be up to no good. You must be either mistreating your employees or cheating your customers or both. … And, of course, their ever-helpful approach to this is the reason we’re having such a difficult time coming out of this economic slowdown.”

McConnell said this administration is the most anti-business since President Jimmy Carter’s. “At least you can say this for President Carter: He was largely incompetent. This administration has actually done a lot of damage to the country.”

Sen. John Thune said that in private business, some companies fail. The South Dakota Republican said the Obama campaign focusing on a few failing companies in Romney’s larger record shows he misunderstands capitalism. “You’re not going to win every one,” he said.

Obama’s approach, meanwhile, has led to failures such as Solyndra, Thune said. “His approach is always predicated on the government picking winners and losers. You are going to get more Solyndras because you don’t have that market discipline.”

But don’t expect the issue to go away anytime soon. Obama said on Monday that the campaign would be about the Bain issue, and it is a key part of his campaign’s strategy through Election Day.

In a briefing on condition that they not be directly quoted, senior administration officials said the campaign plans to build the story over time as the election approaches, and the narrative will center on whom middle-class families can trust in the Oval Office. The officials said there was no concern that Obama would get tagged as practicing the politics of personal destruction, saying that Romney’s record as a businessman is a legitimate line of attack.

Pundits on MSNBC’s “Morning Joe” may have an issue with the Bain attacks, but the American people find them very relevant, one official said.

The official also said Romney would not be allowed to Etch A Sketch his way out of his Massachusetts record, charging that it was a disaster for job growth.

The White House officials denied that there was a falling-out with Booker, and Booker has said he was not specifically asked to walk back his Sunday comments.

Republicans accused Democrats of trying to cover up efforts to muzzle Booker.

“This entire episode demonstrates just how far the Obama campaign will go to punish Democrats who speak out on behalf of job creators and the free enterprise system,” Republican National Committee Chairman Reince Priebus said.