(CNN) Democrats who hadn't had much to celebrate over the past two years two-stepped and toasted their return to relevance on Capitol Hill in the basement of a Washington hotel on Tuesday night.

For the first time in eight years, they had regained the majority in the House of Representatives. When the next Congress arrives in Washington, Democrats will be wielding the House gavels with a mandate to grind President Donald Trump's agenda to a halt.

"Remember this feeling, know the power to win," House Minority Leader -- and potentially House speaker in waiting -- Nancy Pelosi told an audience that cheered "speaker, speaker, speaker" for her as she took the stage. "Thanks to you we owned the ground. Thanks to you tomorrow will be a new day in America."

Across the aisle, Republicans working on House races who had projected confidence throughout the 2018 cycle dropped the pretense early in the night.

Asked what they planned to drink to mark the end of the campaign, one Republican working on House races deadpanned: "Paint thinners."

It was a rare triumphant night for the Democratic Party, which has been hell-bent on taking back the House since Trump won the presidency and Republicans began hacking away at his predecessor's legacy. It was driven largely by a revolt against Trump in the suburbs, where Democrats picked up race after race Tuesday night on their march to the majority.

A turbo-charged ground game was key, but the reality of why Democrats won the House is more complicated: Unlike the more centrally organized Senate and governor's races, the party's tactics for reclaiming the chamber were mostly handed up from the grassroots, which backed hyper-local, moderate candidates in districts that voted for Trump, while leaning on first-time candidates, most of them women and military veterans, in swing seat races.

Their new capacity, though, comes with a slew of unresolved and potentially divisive strategic questions. On the campaign trail, Democrats promised to both run down corruption in the White House -- using the majority's subpoena power -- while working to protect and expand a health care system Republicans remain committed to dismantling.

But striking a balance that satisfies the party's "resistance" base, its vocal crop of progressive insurgents and the entrenched powerbrokers threatens to bedevil, and potentially handcuff, the next speaker, whether it's a seasoned operator like Pelosi or a new leader on a short honeymoon.

On the Republican side, losses in the suburbs of Washington, Philadelphia and Denver were expected, but the real Republican hand-wringing began when seats began to fall in Dallas, Kansas City and Charleston, South Carolina.

Some operatives blamed historical norms -- the party out of presidential power usually picks up seats in the first midterm after losing the White House -- while others pointed to Trump's insistence on mostly ignoring the economy in favor of scare tactics on immigration. The 11th-hour chatter about ending birthright citizenship by executive order, they groused, wasn't winning over any cautious moderates.

Others cited the unease created by the national focus on 14 pipe bombs sent to prominent Democrats and CNN over five days and the killing of 11 congregants at a synagogue in suburban Pittsburgh late last month.

"That's when the momentum was blunted and shifts in polling began to occur," said a top Republican operative working on the midterms. "Rightly or wrongly, the media labeled Trump as culpable for what occurred and that buried Republicans in suburbs where the professional class is fed up with that strain in our country."

It was particularly potent, the operative concluded, in Virginia, Illinois and South Florida, all home to some of Democrats' biggest House wins.

By contrast, the midterms for Democrats -- from start to finish and with limited interruptions -- were almost entirely about health care.

Democrats ran 752,000 ads, or 53% of its total for the year, on health care, according to data from CMAG. That number went up in the final month of the campaign, too, with a staggering 58% of all Democratic campaign spots focused on that singular issue.

Republican messaging was scattershot, according to CMAG, with taxes the focus of a third of GOP ads, but there was far less primacy -- health care and immigration were also about 20%. And in the final month of the campaign, Republicans actually scaled back on health care messaging, only making the issue the focus of 31% of their ads.

But even as Trump's messaging complicated House races, it proved potent in the Senate.

The forces that alienated suburban voters -- Brett Kavanaugh's Supreme Court nomination and Trump's racist rhetoric on immigration, in particular -- fueled a GOP surge in states Trump won in 2016, and where he campaigned for Republican candidates in the closing weeks of the campaign.

Democrats thought getting former Gov. Phil Bredesen, their best-known and most popular possible recruit, into Tennessee's Senate race would make it competitive. But Republican Rep. Marsha Blackburn ran away with the race by more than 10 percentage points.

They thought Indiana Sen. Joe Donnelly and Missouri Sen. Claire McCaskill both stood strong chances of holding onto their seats in states Trump won by nearly 20 points in 2016. Both were easily dispatched. Sen. Heidi Heitkamp was easily ousted in North Dakota.

The party was once again bedeviled by Florida, where Republican Gov. Rick Scott led Democratic Sen. Bill Nelson in a race Democrats thought they had steered to a narrow victory. The real heartbreaker for liberals in Florida and around the country, though, came in the governor's race, where former Republican Rep. Ron DeSantis narrowly defeated Democrat Andrew Gillum, who was vying to become the state's first black governor.

DeSantis closely aligned himself with Trump; Gillum ran on progressive populism. It looked to many like a preview of the 2020 presidential race. And DeSantis won it.

Most ominous for Democrats: Trump proved to be a potent force whose popularity with conservatives is durable.

Trump blanketed the country in 2018, traveling to 23 states for 43 rallies. And in the final six days of the 2018 midterms, Trump headlined 11 rallies in eight states. He visited Georgia, Florida, Tennessee, Ohio, Indiana, Missouri, West Virginia and Montana.

Republicans notched major statewide victories in all but West Virginia and Montana.

But Trump's impact on races, especially in the House, was not universally positive. Many House races that Democrats won on Tuesday night came in the suburbs of America's largest cities, where Trump's rhetoric and style are deeply unpopular.

"It is a double-edged sword," one Republican official said of the presidential visits.

For newly empowered Democrats, there is also a piper to pay.

"It's a totally different game. What we get to do is go from two years of defense to finally getting to go on offense," Ezra Levin, co-founder of Indivisible, the powerful activist network formed after Trump's election, said on Tuesday night.

The group will soon roll out a fresh guide to help its members navigate the new balance of power and pressure Democratic allies in Congress to follow through on their campaign promises.

"Democrats will need some encouragement, some friendly encouragement from the folks that put them in office," he said.

Ethan Todras-Whitehill, executive director of Swing Left, which raised more than $10 million from over 73,000 grassroots donors for House candidates, said he believes the lessons of 2018 can change the way Democrats run campaigns. But only if the party continues to directly engage and even challenge its hyper-charged new activist class.

"The people who are listening to Swing Left and Indivisible are probably pretty likely voters in the first place," Todras-Whitehill said. "You have the 15% of the country that's really upset about Trump and wants to do something about it. You don't ask those people to vote. You ask them to do more."

Democrats were skittish on Tuesday night, seeing every loss as a sign of 2016 redux, where they were heartbroken by the results in state after state and, eventually, a Clinton loss.

Those feelings were not helped at the Democratic party when "Fight Song" -- the anthem synonymous with Hillary Clinton's failed 2016 campaign -- briefly played as worried Democrats ambled into the ballroom.

"It," a Democratic aide said as he walked away from the night's playlist, "has been handled."

And later that night -- as Democrats toasted to Beyonce's "Run the World" after winning the House -- it actually had been.