(CNN) President Donald Trump demolished the "blue wall" in the Great Lakes region two years ago. On Tuesday night, Democrats rebuilt it.

The party's candidates won races for governor and the Senate in the three states that delivered Trump the presidency -- Michigan, Pennsylvania and Wisconsin. Democrats padded their new House majority in the suburbs of Philadelphia and Detroit, while Milwaukee delivered the surge they needed to finally, on their fourth try, beat Republican Gov. Scott Walker.

The Democratic victories set the stage for a 2020 battle royale in the three states that could decide the presidency.

They could also shape a Democratic nominating contest set to begin almost immediately, underscoring which states Democrats are best poised to win and which candidates and issues most appeal in those states.

It's a dynamic that Ohio Sen. Sherrod Brown, a populist Democrat with Midwestern appeal who was re-elected Tuesday night, sought to tap into almost immediately with a victory speech that foreshadowed a potential presidential run when he called his win "the blueprint for our nation in 2020."

"Let our country -- our nation's citizens, our Democratic Party, my fellow elected officials all over the country -- let them all cast their eyes toward the heartland, to the industrial Midwest," he said.

The recipe for a Democratic comeback in the Great Lakes region was straightforward. Candidates largely ignored Trump. Instead, they focused on health care as well as bread-and-butter budget issues like funding for schools, roads and infrastructure.

They also capitalized on a reality that didn't end when Trump took office: Voters are still angry, they're eager to assign blame, and Barack Obama is no longer around to shoulder it.

Republicans have dominated governors' offices and legislatures in the Midwest for most of the last decade. Following the template set by former Indiana Gov. Mitch Daniels, they've largely governed on an agenda of budget austerity -- which has been met with occasional protests over funding for education and infrastructure.

Voters appear to have reached a breaking point. A Marquette Law School poll in October found Wisconsin voters would, by a 57% to 37% margin, rather increase spending on public schools than reduce their property taxes.

Trump's message of scrapped trade deals and rebuilt roads and bridges appealed to voters who have watched their region's manufacturing base crumble in recent decades. But the gains those voters expected have largely not materialized under Trump, and frustrations over issues such as stalled funding for schools and still-rising health insurance premiums have mounted. With Obama no longer in office and Hillary Clinton off the political stage, there's no one to blame but Republicans.

Gretchen Whitmer on the campaign trail in June.

"You can't say government is terrible if your party's in control of it," Gretchen Whitmer, the Democratic governor-elect of Michigan, said in an interview.

The 47-year-old Whitmer -- who some Democratic strategists said was the party's best candidate this year -- could be the biggest star in Tuesday's crop of winners.

She campaigned on a simple, blunt slogan: "Fix the damn roads." The slogan was more than a literal call to fill the potholes that forced Whitmer to replace two car windshields during the campaign -- and it tapped into something that party strategists said was at the core of their resurgence.

On the campaign trail, people frequently shouted takes on Whitmer's slogan at her. "Fix the damn schools" and "fix the damn water" were two of the most common variations, she said.

"It touches people at that nerve where they feel it, right? But also it points directly to what state government's supposed to be doing," Whitmer said.

In Wisconsin, rising Democratic star Josh Kaul leads a razor-tight race for attorney general. He echoed Whitmer, saying voters are worried about an opioid crisis, environmental catastrophes especially in water infrastructure, school safety and more.

"I think that there is a sense that people want new leadership, they want a change of direction. And right now, Republicans are in control of the governor's office of Wisconsin, the state legislature, the attorney general's office, certainly Donald Trump is the president," he said.

Early signs of a Democratic resurgence came in special elections in Wisconsin and Pennsylvania. And Walker -- a battle-tested Republican who had built an effective political machine in Wisconsin -- saw it coming.

In January, he warned that a state senate special election victory by Democrats was "a wake up call for Republicans in Wisconsin." When the liberal candidate won a state Supreme Court seat in April, Walker tweeted that "we are at risk of a #BlueWave."

But the most significant sign of all came in April, when Democrat Conor Lamb won a special congressional election for a heavily Republican district outside Pittsburgh.

"The Conor Lamb victory really kind of painted a roadmap," said Mike Mikus, a Democratic strategist in western Pennsylvania. "What that told me there was a big enough group of people that liked Trump but still considered themselves Democrats. That was the building block."

Mikus said Democrats in 2016 watched counties that they'd always lost slip -- with their share of the vote plummeting from the mid-40s to the low-30s. That gap couldn't be overcome in Philadelphia and Pittsburgh alone.

He said Gov. Tom Wolf's persistence working for economic opportunity for those rural areas, as well as Sen. Bob Casey's focus on pensions and health care for retired miners, were part of why those Democrats cruised to re-election in 2018 without facing serious challenges.

"What I think a lot of people missed is there was a heck of a lot of voters that didn't like Trump, didn't like Hillary, and they ended up voting for Trump," he said. "You have to give them a reason to come back."