Attorney General Lori Swanson issued an opinion Thursday that state Sen. Michelle Fischbach, who is slated to become Minnesota’s lieutenant governor in January, would violate the Minnesota Constitution if she tries to simultaneously stay in the Senate.

“Potential conflicts exist if the same individual were to fulfill both executive and legislative responsibilities,” reads the opinion, signed by Solicitor General Alan Gilbert. He notes that Minnesota courts would have to make the ultimate determination.

The opinion sets up a likely lawsuit, with Senate DFLers trying to eject Republican Fischbach from the Senate, citing the Constitution’s ban on legislators holding “any other office.” But Senate Majority Leader Paul Gazelka, who wants to keep Fischbach in the Senate, dismissed Swanson’s opinion.

“We just received the opinion of Solicitor General Gilbert, and it’s just that — an opinion,” Gazelka said, highlighting that such opinions are not legally binding like those of a judge. He noted that the Senate’s own counsel has issued his own opinion that Fischbach can occupy both seats.

Fischbach’s decision to try to hold both offices promises to be hugely consequential at the State Capitol. Republicans now control the Senate by a margin of 34-32, with one seat vacant. If the DFL can hold a seat in the southeast metro to replace recently departed DFL Sen. Dan Schoen in a Feb. 12 special election, and then win a subsequent special election to replace Fischbach, they would take over the majority.

DFL Gov. Mark Dayton said Thursday that he would not call a special election to replace Fischbach until she resigns her legislative seat.

But Fischbach, a Paynesville Republican, has said she will not resign.

Fischbach’s St. Cloud-area district has been solidly Republican, but DFLers would still be likely to see a special election as a big opportunity: Around the country, Democrats have been winning special elections in recent months as their voters have been energized by anger at Republican control in Washington.

None of that is possible, however, if Dayton doesn’t call an election to replace his new Republican lieutenant governor: “That’s a matter for the Senate to resolve within itself and for the courts to resolve if the Senate is unable to do so,” Dayton said Thursday at what’s likely to be his last news conference of the year.

Fischbach’s ascension to lieutenant governor is the culmination of an unexpected series of events related to the wave of women coming forward to allege improper conduct by powerful men. Last week, Dayton appointed his current lieutenant governor, Tina Smith, to replace Sen. Al Franken in the U.S. Senate after he was accused by more than half a dozen women of touching them inappropriately in photo opportunities and other events.

The special election to replace Schoen in February comes after his own resignation after multiple women alleged he sexually harassed them, which he denied.

Dayton’s refusal to get involved makes it likely that Senate DFLers and/or a Fischbach constituent would launch a lawsuit trying to remove her.

“We appreciate Governor Dayton letting the Senate figure this out. I remain open to a smoother transition plan that elevates a member of the governor’s own party to the lieutenant governor position,” said Gazelka, R-Nisswa. But if that doesn’t happen, he said following the attorney general’s opinion, “I have every confidence Senator Fischbach will continue to be an effective public servant for her constituents in her roles as a state senator … and acting lieutenant governor.”

Senate Minority Leader Tom Bakk, DFL-Cook, said he agreed with Swanson’s opinion. He raised the prospect that Fischbach’s Senate votes would not be legitimate.

“I respectfully request that Sen. Fischbach consider this advisory opinion very seriously,” Bakk said. “I have concerns with the validity of votes cast during the legislative session if Sen. Fischbach continues to pursue serving in both the executive branch and the Legislature.”

With Swanson’s office finding that Fischbach is in violation of the Constitution, “it seems like there would be a legal challenge,” Bakk said.

This would be the second time in less than a year that leaders in Minnesota state government have thrown a weighty constitutional conflict to the courts after failing to resolve their differences. Dayton prevailed over the Legislature at the Supreme Court after vetoing its funding last spring.

Staff writer Jessie Van Berkel contributed to this report.