As the U.S. Department of Justice continues to probe the relationship between North Carolina Gov. Pat McCrory's (R) administration and Duke Energy following the company's massive coal ash spill into the Dan River, a campaign finance watchdog group has released a report putting the utility's investments in McCrory's political career into eye-opening national context.

This week the National Institute on Money in State Politics (NIMSP) released an analysis of direct contributions to gubernatorial campaigns nationwide from Duke Energy's political action committee and company executives from 2000 through 2012 -- and found that McCrory received three times more than five other sitting governors combined.

Besides McCrory, the other current governors who received contributions from Duke Energy's PAC and/or executives since 2000 are Steve Beshear (D-Ky.), Sam Brownback (R-Kan.), Nikki Haley (R-S.C.), John Kasich (R-Ohio), and Mike Pence (R-Ind.). Duke Energy has operations in all of those states.

Duke Energy's PAC contributed a total of $30,000 to five of those governors (all but Kasich), with $16,000 of that going to McCrory, according to NIMSP. In addition, the company's executive officers contributed a total of $94,750 to four of those governors (all but Brownback and Haley), with $82,000 of that -- 87 percent -- going to McCrory.

"While Duke Energy was a generous donor to McCrory, it will be up to a federal grand jury to determine the extent to which their relationship affected the regulatory actions taken over Duke's multi-million-gallon spill into the Dan River," wrote NIMSP's Gus Voss.

McCrory worked for Charlotte, N.C.-based Duke for 28 years before leaving the company for his first unsuccessful run for governor in 2008. He ran again in 2012 and won.

Other analyses have turned up even larger figures for Duke Energy's giving to McCrory, in part because they included donations from North Carolina-based Progress Energy, which is now a Duke subsidiary. For example, a 2013 report by the campaign finance watchdog group Democracy North Carolina found McCrory received over $300,000 in direct contributions for his 2008 and 2012 gubernatorial campaigns from Duke/Progress-related donors. In addition, Duke/Progress gave an additional $761,800 to the Republican Governors Association, a major GOP committee that helped McCrory's campaign.

And earlier this year, Democracy North Carolina released a follow-up report that detailed an additional $437,000 in contributions from Duke/Progress donors to Republican causes in 2013. Meanwhile, how much the company may have contributed to Renew North Carolina, a pro-McCrory shadow campaign committee, is not known because the 501(c)(4) nonprofit is not legally required to disclose its donors and to date has not done so voluntarily.

Duke Energy, which became the nation's largest utility following its merger with Progress Energy, has also contributed over $1 million to the campaigns of North Carolina lawmakers. In addition, a recent analysis by Facing South revealed the company contributed $175,000 to a Washington, D.C.-based Republican super PAC that played a major role in a 2012 North Carolina Supreme Court race. Duke Energy is current embroiled in two legal controversies -- one over cleaning up its coal ash and the other over its merger with Progress Energy -- that could eventually end up before the state's high court.

McCrory has come under fire for his cozy relationship with Duke Energy and the "sweetheart deal" his administration struck with the company over its coal ash pollution even before the Dan River spill. In addition to receiving generous campaign contributions from Duke, McCrory continues to hold significant investments in the company, and his administration has close ties to the utility.

"People are tired of big money buying special treatment," Democracy North Carolina Executive Director Bob Hall said. "Duke's use of campaign donations to buy protection from regulators needs to be fully examined."

McCrory has even faced criticism from lawmakers in his own party recently for going easy on Duke Energy. State Sen. Tom Apodaca and Rep. Chuck McGrady, Republicans representing Western North Carolina districts where a massive Duke coal ash impoundment is leaking toxins to the environment, expressed displeasure after McCrory unexpectedly announced last week that he would seek legislation for coal ash oversight that's not as strong as a proposal they had been working on with him.

McGrady, a former national Sierra Club president, told The News & Record of Greensboro, N.C. that McCrory's surprise proposal "doesn't feel like a collaborative effort."