Wisconsin Gov. Scott Walker (R) has been billing himself as the “education governor,” although his Democratic opponents disagree. (Elizabeth Flores/Star Tribune/AP)

Gov. Scott Walker became one of the country’s biggest Republican stars by battling labor unions and fending off a recall campaign amid mass protests at the state Capitol.

But as a crowded field of Democrats competes in Tuesday’s primary to challenge Walker again in November, the governor has struggled to find his path in a fast-changing GOP.

Walker, 50, like many Republicans whose national aspirations were upended by Donald Trump, failed to gain traction in the 2016 presidential race. Then he watched as Trump became the first Republican presidential candidate since Ronald Reagan to win Wisconsin, effectively transforming the tea-party network that once bolstered Walker into the core of Trump’s unpredictable base.

Lately, Walker has taken to billing himself as the “education governor,” provoking outrage from Democrats who note he oversaw years of stagnant funding for public schools. He has largely abandoned his slams on former president Barack Obama’s health-care law. And he rarely mentions one of his signature achievements — passage of the controversial 2011 law that shattered public employees’ union powers.

“In 2014 we reacted to what people were asking about then and two years ago we began listening sessions in every county,” Walker said, acknowledging that his 2018 campaign has emphasized different issues than his past races, “and these are things you hear about.”

Walker kicked off a six-day, 21-stop bus tour late last week by stressing the state’s 2.9 percent unemployment rate and his success at balancing the state budget.

“Wisconsin is working again,” Walker told three dozen steelworkers at a Milwaukee plant on Thursday. “There are more people in the workforce in Wisconsin than ever before in the history of the state.”

Walker, nonetheless, must overcome a sense here that voters have grown concerned about whether the state needs to do more to fix struggling schools and roads.

In his past races here, including the 2012 recall effort, Walker narrowly prevailed after building support from a coalition of suburban professionals, farmers and factory workers behind his message of keeping the budget lean. As he eyed the White House, Walker also pushed Wisconsin into the forefront of nationally focused conservative causes, including voter identification laws and loosening environmental regulations.

Amid uncertainty over how Trump’s bombastic presidency would translate to the 2018 elections here, Walker has been trying to insulate himself from a potential Democratic onslaught.

In April, after Democrats won a hard-fought race for a state Supreme Court seat, Walker tweeted that he was likely to face a “blue wave” this year. More recently, he’s blasting donors with appeals citing various public opinion polls that show a Democratic challenger as much as 13 points ahead.

In a sign of just how competitive the race could be, the Republican Governors Association has reserved $5.1 million in television ad spending here. Last month, the Democratic Governors Association announced it had reserved $3.8 million in airtime.

“This the first year he’s running in a midterm with partisan national head winds against him,” said Charles Franklin, director of the Marquette Law School Poll, the state’s preeminent survey. “He doesn’t have Obama to light Republicans like each of his previous races, and if those national forces cost him just 1 to 2 percent of the vote, that would put him in a very, very close race.”

In Walker’s past races, Franklin noted, the electorate was evenly split between those voters who prioritized education vs. those who favored cuts in local property taxes. Now, about 60 percent of Wisconsin voters favor more spending on education while just 35 percent say they would prioritize additional property tax cuts, he said.

Bob Dohnal, a veteran activist and publisher of the Wisconsin Conservative Digest, said the shifting public attitudes toward spending reflect a broader disintegration of the state’s tea-party movement. At its peak around 2010, Dohnal said 143 tea-party chapters had 150,000 members in Wisconsin. Today, Dohnal says he doesn’t think even one of them remains active.

What remains of the movement, Dohnal said, has been swept into Trump’s more populist army. That message still centers on keeping taxes low but also includes calls for spending money on roads and bridges, he added.

“You have to govern the state because you are not an anarchist,” said Van Mobley, one of Trump’s earliest and most visible Wisconsin supporters. “Walker’s earlier focus was that spending was out of control but now, in many ways, it’s now going to be making sure that you have institutions that are going to work.”

Republican strategists say Walker’s challenge will be finding ways to rally Trump voters while also recasting himself into the mold of traditional, Midwestern Republican governors who governed with a softer edge.

“The message is investment in education, and it is jobs,” said John Schulze of the Wisconsin Association of Builders and Contractors.

Some Walker critics are seizing on the issue. One union representing highway engineers erected billboards throughout the state showing an image of Walker sticking out of a pothole below the phrase, “Pardon Our Scott-Holes.”

In recent weeks, Walker has blanketed the airwaves touting the groundbreaking of the new mega-plant for Foxconn, a Taiwanese electronics manufacturer. The plant in southeastern Wisconsin is slated to create up to 13,000 new jobs, but Walker has faced withering criticism for agreeing to $3 billion in subsidies.

But Walker has signaled that he will rely on more than an economic message to energize Republicans.

At a news conference last week with Milwaukee police, and again on his bus tour, Walker attacked the Democratic candidates over calls to reduce the incarceration rate. In a return to 1990s-style GOP messaging, Walker warned that thousands of violent offenders would be released.

“I want to keep them in for their full terms,” said Walker, standing in front of photographs of three men convicted of murder or sexual assault. “Many of the Democrats want to let them out early.”

Wisconsin Democrats’ most immediate challenge is choosing their nominee, a process that threatens to undercut party unity.

Although eight candidates remain in the race, many Democratic operatives and activists believe that only three have credible paths to victory.

Polls show Tony Evers, the three-term state schools superintendent, is the front-runner. If he wins, an Evers-Walker race would become a showdown over Wisconsin’s spending on public education.

But some Democrats wonder whether Evers, 66, is inspirational enough to lead the party to victory. Those concerns reflect the broader debate within the Democratic Party over how best to drive young voters and minorities to the polls.

“He’s the same retread of the candidates that we’ve run in the past,” said Mahlon Mitchell, 41, who is president of the Professional Fire Fighters of Wisconsin and would become the state’s first black governor. “You can talk about a ‘blue wave’ . . . but you can’t just go up against [Walker] with the same old rhetoric.”

Kelda Roys, a former state legislator backed by NARAL and Emily’s List, also argues that she could put together a more effective Democratic coalition. She made national headlines in March by breast-feeding her baby in a campaign ad.

“We can get the real swing voters in Wisconsin, who are suburban married women, if we have a candidate they can relate to,” Roys, 39, said.

Here in Oshkosh in Winnebago County, voters said they are slowly starting to think ahead to the general election. Walker, Obama and Trump all carried this swing county in their respective races.

At Friar Tuck’s restaurant, known for its $7 roast beef sandwiches and leather-backed bar stools, Jo Ann Beck said she supports Walker because she feels the state’s economy is back on track.

“I wasn’t happy he went after the unions, but I have grown to like him,” said Beck, 74, a retired school library aide who also plans to cast her vote in support of Trump.

In downtown Oshkosh, Trump is also helping to decide Jean Erdman’s choice for governor. Erdman, a retired professor, was so “heartbroken” over Trump’s victory she now shows up almost daily to volunteer at county Democratic headquarters.

Since the start of the year, the party’s volunteer pool has grown by a third to 200, and the office is adorned with hand-painted “A blue wave is coming” signs.

“I just feel we are better than this,” said Erdman, adding she thinks Walker’s battles with unions in 2011 led to a corrosive political environment that formed the foundation for Trump’s victory. “And I wouldn’t be here if I thought it would be easy to take on Scott Walker.”