ST. PAUL, Minn. – Minnesota Gov. Mark Dayton appointed Lt. Gov. Tina Smith on Wednesday to replace fellow Democrat Al Franken’s Senate seat until a special election in November, setting up his longtime and trusted adviser for a potentially bruising 2018 election.

Smith was widely seen as Dayton’s top choice from the moment Franken announced his resignation last week. But her previous decision not to run for governor had raised questions about whether she would want to launch a Senate campaign that would be in the national spotlight.

Smith told reporters she will run in next year’s election to complete Franken’s term through 2020, stressing that she’s ready for the challenge and national spotlight that awaits.

“I can tell you I shouldn’t be underestimated and if I weren’t confident I wouldn’t be doing this,” she said.

It’s not clear when Smith will head to Washington. Franken, who resigned under pressure from his own party after he was accused of improper behavior by at least eight women, announced last Thursday that he would resign “in the coming weeks.”

But his office hasn’t set a final departure date yet. Smith indicated it would likely be in early January.

Smith will be the second Democrat to make way for the Senate in as many days, after Doug Jones’ victory in Alabama in Tuesday’s special election. Smith’s appointment won’t change the balance of power in the Senate.

Smith, 59, served as Dayton’s trusted chief of staff for four years before ascending to become his No. 2 when he needed a running mate in 2014. Dayton has long treated her as an equal in the office, and it was that deference that fueled speculation she was being groomed to succeed him.

Her path to politics was unconventional. A native of New Mexico, she graduated from Stanford and earned an MBA from Dartmouth. A marketing job with General Mills brought her to Minnesota, where she eventually started her own marketing and political consulting firm.

She managed Ted Mondale’s unsuccessful campaign for governor in 1998, then ran the short-lived 2002 Senate campaign for his dad, former Vice President Walter Mondale. Smith served as chief of staff to Minneapolis Mayor R.T. Rybak before eventually taking the same job with Dayton in 2011.

Smith, a soft-spoken, smiling presence at the Capitol, is credited with playing quiet but key roles in the response to the 2007 bridge collapse in Minneapolis and in the building of a new Vikings stadium. Dayton made her his point person on a massive public-private partnership to work with Mayo Clinic on an ambitious expansion in Rochester.

Next year’s race to fill the final two years of Franken’s term is certain to be one of the nation’s most closely watched and expensive, and Dayton was under pressure from fellow Democrats in Washington to ensure his pick would use the appointment as a springboard for that election. Republicans immediately floated former two-term Gov. Tim Pawlenty as a possible candidate, but many others were said to be weighing a race.

Republicans immediately pounced on Smith’s appointment Wednesday morning, suggesting that Dayton’s selection and a runway to the 2018 campaign could upset voters.

“Minnesota voters deserve a Senator who will look out for their best interests, not another DFL (Democratic-Farmer-Labor Party) insider handpicked by Mark Dayton,” National Republican Senatorial Committee spokesman Michael McAdams said in a written statement.

And Smith’s past work with Planned Parenthood in Minnesota and other Midwestern states, which provides abortions along with other health services, was sure to become a flash point with Republicans on the campaign trail.

Smith, who served as an executive, said Planned Parenthood provides critical health care and sexual transmitted disease treatment to “thousands and thousands and thousands of women.”

“I’m proud of that work,” Smith said.