(Photo by Will Stone - KJZZ)

Democratic Arizona Corporation Commission candidates Bill Mundell and Tom Chabin.

The two Democrats running for Arizona corporation commission say the head of the state’s largest utility has created a “culture of corruption” and the uility could be connected to "dark money" spending this election.

On Monday, commission candidates Bill Mundell and Tom Chabin fired back at the leadership of Arizona Public Service (APS) after learning its CEO Don Brandt sent an email to employees encouraging them to vote for the three Republicans in the race — Andy Tobin, Boyd Dunn and Bob Burns.

Brandt also wrote Mundell and Chabin could not be impartial if elected based on their criticism of the utility throughout the campaign.

“No other utility in the state of Arizona has made any endorsement of any candidates except for APS,” Chabin said. “We know that every time a customer paid their bill in the past, a little bit of that money went to dark money campaigns that elected commissioners two years ago.”

Brandt’s endorsement of Commissioner Burns is particularly surprising given that he has led the fight to force APS to disclose whether it was behind $3.2 million in dark money spending last election.

The utility’s alleged 2014 campaign spending isn’t the only source of concern for the two Democrats.

Recently, the political committee associated with the Arizona Association of Realtors launched a website and sent mailers endorsing the three Republicans. Campaign finance reports show the group has $1 million on hand to spend this cycle.

“Why would they want to participate in a commission race? The concern is disclosure. Did APS funnel or launder money to the realtors to spend in this race?,” Mundell said on Monday, adding that the realtors have not traditionally invested in commission races.

The solar industry has not sat on the sidelines of this year’s election, either.

National rooftop solar leasing company Solar City, which is typically at odds with APS over solar policies like net-metering, recently advised its customers to vote for Mundell, Chabin and Burns. The company has also indirectly funneled about $800,000 into this race through independent expenditures to support its three preferred candidates.

Mundell and Chabin have proposed a “code of ethics” based on the behavior that has occurred at the commission over the last two years.

APS does not discuss campaign finance questions.

The Arizona Association of Realtors has not yet commented on Mundell's statements.