Gov. Mark Dayton broke state law by bringing a campaign staffer along on the state plane for a 2012 trip to promote DFL candidates, according to a long-awaited audit released Thursday.

"Since the campaign official did not travel with the Governor to participate in state government business, it was a violation of state law and (Minnesota Department of Transportation) policy for the campaign official to travel on the state airplane," said the report from the Minnesota legislative auditor.

Dayton's political use of the state plane has been under scrutiny for more than a year. Shortly before the election that gave Democrats control of the Legislature in 2012, Dayton took three trips to outstate Minnesota that combined political and official purposes. On one of those, his campaign staffer, Julie Hottinger, traveled with him.

In response to the auditor's finding, Dayton's chief of staff, Tina Smith, acknowledged that the governor made a mistake in having Hottinger accompany him on the state plane to Bemidji and International Falls before the 2012 election.

"This was an error and will not happen again," Smith said.

In the absence of clear state legislation to guide them, she said the Dayton administration established a policy of repaying the state for any political travel on the state plane on a prorated basis. She said the policy was modeled after the long-used White House policy for use of Air Force One.

Dayton

The legislative auditor found that Dayton's occasional campaign use of the state plane in itself did not necessarily constitute a legal or policy violation.

"The state has not established a consistent standard for determining whether it is lawful for the Governor to use a state airplane to travel to political events," the audit said. Between January 2011 and June 2013, Dayton took 55 trips on the state plane. Only the three flights in late 2012 were deemed to have political components.

The auditor recommended the Legislature clarify the law regarding the use of the plane for politics.

Common Cause Minnesota and the Minnesota Jobs Coalition joined together on Thursday to call for a starker division between campaigning and governing.

"A clear line must be drawn between campaigning for re-election and serving the people of Minnesota. It is disappointing that the Office of Gov. Dayton blurred that line," said Jeremy Schroeder, executive director of Common Cause Minnesota.

In response to a complaint from the Republican-led Minnesota Jobs Coalition, another state watchdog had already examined Dayton's 2012 flights. In September, the state's campaign finance agency found Dayton violated the law by not disclosing his campaign debt for his political use of the state plane for those trips. In part because the media had reported on Dayton's plan to repay the state, however, the board decided that the lack of disclosure was inadvertent and did not merit a fine.

Smith, the governor's chief of staff, said that unless instructed otherwise, Dayton would continue to have his campaign reimburse the state for any political portion of plane travel and for all car travel to political events.

The governor's staff has said Dayton did nothing wrong in flying to the 2012 political events in Willmar, Brainerd, Bemidji and International Falls, but working papers the auditor gathered reveal there was some discussion of whether the trips were appropriate.

According to the working papers, Paula Brown, Dayton's director of operations, told the auditor late last year that "she did talk to senior staff last fall about the 'public perception' of these flights."

Dayton has not repaid the state for any additional state plane trips since he made reimbursements for the three flights from 2012, nor has he taken any high-profile flights combining politics and official business. Smith said his campaign has reimbursed the state for all 2013 car trips that included political events.

Previous governors have been scrutinized for their private use of state resources but not, in recent history, for their plane travel.

In 1999, then-Gov. Jesse Ventura's use of state security protection while on his book tour was put under the microscope. There are no major records about Republican Gov. Tim Pawlenty, who preceded Dayton, using the state plane for political purposes during his eight years in office. In 2008, Pawlenty did reimburse the state for $910 for car mileage through his campaign committee.

Sen. Dave Thompson, one of several Republicans vying for Dayton's job, said "the governor should have been more careful." But, he said, he was not planning to throw stones at Dayton because of the apparent violation, nor did he plan to pursue legislation to clarify the law.

Of the legal violation the auditor highlighted, spokesman for the Ramsey County Attorney Dennis Gerhardstein said: "Our office would certainly review any case that is brought to our attention by law enforcement."

Pro bono became $77,000 bill

The audit also revealed that attorney David Lillehaug, the special counsel advising Dayton during the 2011 shutdown, did not end up working pro bono as the governor had announced at the time.

"In August 2011, the Governor signed an amendment that changed the engagement from pro bono to billable services," the legislative auditor's report said. "The office paid the firm about $77,000 for those services."

Dayton's communications director Bob Hume on Thursday said the governor's arrangement with Lillehaug went from pro bono to paid after Lillehaug's role dramatically expanded as the shutdown wore on.

Lillehaug is a former U.S. attorney who had long represented Democrats, including Dayton, in campaign and election matters. Last year, Dayton appointed Lillehaug to the state Supreme Court.

Hume said that Lillehaug did a "superb job" in handling shutdown-related matters and the state received great value for his service.

"It is a decision we stand by," Hume said.

Rachel E. Stassen-Berger • Twitter: @RachelSB