Republican Lt. Gov. Michelle Fischbach resigned her state Senate seat Friday and took the oath of office as lieutenant governor in the DFL administration of Gov. Mark Dayton.

While Republican Fischbach has held the lieutenant governor post since January, her unexpected resignation from her St. Cloud-area seat left the state Senate split equally between the two parties — 33 Republicans and 33 DFLers. That means political control of that chamber will depend on the outcome of a special election to replace her.

Dayton immediately set that special election for Nov. 6, same as the general election. With an open governor's race and the entire state House on the ballot, it means both political parties now have a path to full control of Minnesota government in 2019.

"I never expected that I would become lieutenant governor, especially this way, but I do appreciate the opportunity," Fisch­bach said Friday following a brief swearing-in ceremony at the State Capitol, with family members and Dayton standing nearby. "This had been a big adventure and will continue to be a big adventure."

Fischbach, who previously fought in court for the right to serve simultaneously as senator and lieutenant governor against a legal challenge by a DFL activist, said the end of the legislative session earlier in the week — and Dayton's pledge that he would not call a special session — prompted her decision.

"I did ascend to the role of lieutenant governor in January, but I would say that I was the acting lieutenant governor and now I'm full lieutenant governor," she said.

Fischbach declined to say whether she would be a running mate to a Republican candidate for governor; of the leading GOP candidates for that seat, only former Gov. Tim Pawlenty has not named his lieutenant governor candidate.

"There's lots of things that go on out there, and right now I'm here to talk about my 22 years of service and becoming lieutenant governor," Fischbach said. "If there's questions about that, there may be other folks you'll want to ask."

Pawlenty's campaign did not return a message Friday seeking comment about his decisionmaking process for that position.

Fischbach ascended to lieutenant governor after Dayton appointed former Lt. Gov. Tina Smith to the U.S. Senate following Al Franken's resignation. As president of the state Senate, Fischbach was next in the line of succession. But her move into the role was complicated by the legal challenge from DFLers, who maintained the state constitution prohibited her from serving in both jobs.

Fischbach's decision brings an end to the legal case over her joint roles. Charlie Nauen, the attorney representing Sauk Rapids resident Destiny Dusosky, a Fischbach constituent who filed two lawsuits on the issue, said he would file Friday to drop the case.

"We are planning to voluntarily dismiss our lawsuit because our relief has been achieved and we're very glad about that," Nauen said.

Dayton said Friday that he and Fischbach have had an "excellent" relationship since she was named lieutenant governor.

He said the two have worked well together on issues including elder care reforms, and he expects they can continue to have a good working relationship, though he doesn't expect they'll agree on all topics.

"When we disagree, we'll disagree," Dayton said. "I think Minnesotans have gotten used to that."

Now, both parties are turning their attention to the special election in Fischbach's Senate district.

The open seat will give the DFL a chance to compete for the Senate majority, though the area has reliably voted Republican in recent years. A spokeswoman for the Senate DFL caucus said her party has already heard from interested candidates.

During her time in the Senate, Fischbach said she's most proud of the work she did on higher education, including helping two-year colleges to secure additional funding from the state.

Star Tribune staff writer Jessie Van Berkel contributed to this report. Erin Golden • 612-673-4790