Democrats were outraged over comments made by one of their own over the weekend when Newark, N.J., Mayor Cory Booker blasted the Obama campaign's attacks on Mitt Romney's private equity career -- possibly one of the easiest and more powerful ways to distinguish President Barack Obama from his Republican rival -- as nauseating.

While the rising political star's comments on NBC's Meet the Press Sunday were paired with reaffirmed support for the president, they were still perceived by many Democrats as a betrayal of both the party and Obama in what is expected to be a razor-close election.

The pressure must have been intense. By Monday, Booker released a YouTube video where he stepped back from his previous statement, instead insisting that it is perfectly reasonable for the Obama campaign to take on Romney's private sector record since he has made his business experience the centerpiece of his presidential campaign.

However, a ThinkProgress investigation has found Booker had good reason to distance himself from the Obama campaign's attacks on Romney's old firm, Bain Capital. According to an examination of New Jersey campaign finance records, Bain Capital was among Booker's earliest and most lavish donors during his first, unsuccessful, run for mayor in 2002, where he received more than $115,000 in contributions from venture capitalists, investors and Wall Street bankers.

Those who reportedly contributed to his campaign included Bain employees John Cannaughton ($2,000), Steve Pagliuca ($2,200) and Jonathan Lavine ($1,000.)

ThinkProgress reports Booker received another $450,000 from the financial sector toward the Booker Team for Newark committee, $15,400 of which came directly from Bain Capital Managing Directors Joshua Bekenstein and Mark Nunnelly.

A confirmation of Booker's 2002 campaign finance records was not immediately available from the New Jersey Election Law Enforcement Commission on Tuesday morning. The agency's website reported technical difficulties on the section containing candidate campaign finance reports.

Bain Capital actually has a history of contributing to Democratic candidates. The company is listed as one of the top overall donors in the 2012 election cycle, expending more than $2.7 million. While the Center for Responsive Politics reports 72 percent of the $756,328 Bain has contributed directly to political campaigns has gone to Democratic candidates, the company has also given a solid $2 million to outside spending groups, all promoting conservative causes.