Friends and associates from Mitt Romney’s business career have donated millions of dollars to help his presidential candidacy, becoming central to a massive network of volunteer fundraisers that has allowed him to raise more money than President Obama in recent months, new records show.

Current and former employees of Bain Capital, Romney’s former private equity company, and the consulting firm Bain & Co. have donated at least $5 million to back the candidate, including funds given to the Republican Party and the independent super PAC supporting him.

The campaign filings come in the midst of an attack from Democrats over Romney’s ties to Bain Capital and reports that it invested in companies that specialized in helping other firms move jobs overseas.

The former Massachusetts governor has cited his experience in the business world, and as the founder and head of Bain Capital in particular, as evidence he would be a better steward of the economy than Obama has been.

Romney recently pulled ahead in the money race, largely because of support from the financial industry. Romney has pledged to extend low tax rates for the rich and repeal the Dodd-Frank financial regulation bill.

Disclosure documents released Sunday night show that Romney’s campaign raised $140 million during the second quarter for Romney Victory, a joint effort with the Republican Party that began in April in April and can accept contributions up to $75,800 from an individual.

Restore Our Future, the super PAC founded by former Romney aides to back his candidacy, raised $20 million in June, an official with the group said. The super PAC has no limitations on the size of donations and its latest haul includes $10 million from one person, casino magnate Sheldon Adelson.

Funding for both groups has been heavily dependent on high-income donors who can cut large checks, a contrast to the Obama campaign’s reliance on large numbers of small donors. About $67 million, nearly half of the funds raised by Romney Victory, have come from donors giving $40,000 or more at a time.

“People who support Mitt Romney do so because they support his pro-growth, pro-jobs agenda for the country,” said Romney spokeswoman Andrea Saul. Officials at Bain Capital did not respond to a request for comment.

Employees of Wall Street titan Goldman Sachs Group gave $902,000 to Romney Victory between April and June, bringing his total from the company to $1.4 million. Donations to the Romney super PAC bring the total to $2.2 million.

The figure from Elliott Management Corporation employees was $895,000. The founder of that hedge fund firm, Paul Singer, is a top fundraiser for Romney and gave $1 million to the candidate’s super PAC. And employees of Blackstone Group, a large private equity company headed by Romney fundraiser Stephen Schwarzman, have given $647,000.

David Beightol, a Romney fundraiser and lobbyist at Dutko Grayling in Washington, said many business and finance leaders support Romney because they oppose Obama’s economic policies and bristle at the president’s “class warfare” attacks.

“The business community understands that Mitt knows what it takes to create a job because he’s done it before,” said Beightol, who has raised at least $180,000, according to disclosure records. “They’re frustrated with the current president because he doesn’t seem to understand what it takes.”

Current employees of Bain Capital have given a total of $1 million and Bain & Co. employees have donated another $280,000. Current employees of Bain Capital have given $1.6 million to the Restore Our Future super PAC, and former employees of both companies have given at least $2.2 million.

Current employees of the two companies have given $158,000 to Obama and the Democratic Party.

New donors listed in Sunday’s report include William Bain, the founder of Bain & Co. who gave Romney his job as head of Bain Capital. Bain gave $50,000 to Romney Victory on top of $2,500 he had already donated to the campaign.

Richard Boyce, a former Bain & Co partner now at TPG Capital, gave $53,300 to Romney Victory and had previously given $100,000 to the Romney super PAC. Records show Boyce’s wife, two children and another relative have also donated to Romney.

Other campaign bundlers with connections to Bain include Steven Barnes, who has donated $200,000, and Edward Han, who works for Bain Capital’s European operation and is co-hosting a fundraiser for Romney during the candidate’s trip to London later this month.

One of the most prominent Romney supporters is Ed Conard, a former managing partner at Bain Capital who has given $73,300 to Romney’s political committees and $1 million to Restore Our Future.

Conard, who recently authored a book espousing conservative economics, said in an interview on MSNBC over the weekend that Romney has “great pride” in his career as co-founder and longtime head of Bain Capital. “I believe these attacks on Mitt and Bain Capital are really attacks on business generally,” he said.

He also said Romney did not have enough money at his disposal to properly respond to the Obama campaign, which has raised more money than Romney overall but has lagged in recent months. “Mitt doesn’t have the money to respond in the ads that really matter, okay?” Conard said. “He can try to make his case in July when nobody is listening to it or he can wait, hold his fire and make his case in September, October, November. I believe he has to make his case.”

Aaron Blake contributed to this report.