CHARLOTTE, N.C. — Republicans went all-in to keep hold of a key congressional district in a special election Tuesday, and they won — but they still have good reason to be concerned about the result.

While the GOP can celebrate the election of a new congressman, Dan Bishop, his 2-point victory in a district President Donald Trump carried by 12 points in 2016 continues a worrisome trend for the party, which suffered heavy losses in the 2018 midterms and has not seen the political environment improve as Trump gears up for reelection.

Trump cannot win a second term without improving his political position, and Democrats know it, casting Bishop’s narrow win as a sign of progress in North Carolina. But Democrats also saw worrying trends of their own on Tuesday, as their candidate Dan McCready benefitted from a surge in metropolitan support that would have brought them victory — if not for an even stronger swell in rural support for Bishop and the GOP.

In short, Tuesday’s results outlined the path to 2020 victory for both parties, cut along the fundamental trend of politics in the Trump era: cities and suburbs swinging more and more Democratic, while the president’s appeal brings exurbs and rural voters deeper into the GOP fold. Trump pushed harder on one side of the scale to win in 2016; Democrats pushed back on the other side to take the House last year. And next year, it will decide whether Trump gets another term or a Democrat takes the White House for four years.

Trump’s election-eve rally for Bishop brought thousands to Fayetteville on Monday night on the eastern edge of the district, and it’s hard to argue with results: McCready had carried the surrounding county, Cumberland County, by more than 4 percentage points last year. But Bishop won it by the narrowest of margins on Tuesday, also making improvements in neighboring counties far from the Charlotte suburbs where McCready was strongest.

“Trump’s support in these mixed rural-suburban districts is really strong,” said David McIntosh, the president of the conservative Club for Growth and a former Indiana congressman.

Republicans agreed the party’s fortunes are tied to Trump’s in 2020 — and argued the results on Tuesday suggested that might not be a bad thing.

“The rest of the party is going to live or die based on how the president, in ’20, performs,” said Patrick Sebastian, a GOP consultant in the state. “If Trump can win North Carolina by a point or two, that’s excellent news for party.”

Meanwhile, Democrats were quick to find the silver lining in McCready’s narrow defeat. Rep. Cheri Bustos (D-Ill.), the chairwoman of the Democratic Congressional Campaign Committee noted that there are nearly three dozen GOP-held House seats that are less Republican-leaning than North Carolina’s 9th District.

“We fell an inch short tonight, but it took more than $6 million in outside Republican spending and a last-minute Trump rally to scrape by in a district that the president carried by 11.9 points,” Bustos said.

Democrats did increase their margins in and around Charlotte in the election, but they were swamped by Bishop’s stronger performance east of the city. McCready won Mecklenburg County, which includes parts of Charlotte and its southern suburbs, 56 percent to 43 percent, up from a 10-point in 2018. Those are some of the same trends that led the party to lose Michigan, Pennsylvania and Wisconsin in the 2016 presidential race, even if stronger numbers in metropolitan areas can put new states on the map for the party.

“If we don’t connect with rural voters — if we don’t show up in 2020 and win these places back — then Trump wins,” Montana Gov. Steve Bullock, a candidate for the Democratic presidential nomination, tweeted late Tuesday night.

Kellyanne Conway, the former GOP campaign pollster working as a counselor to Trump in the White House, touted Trump as the difference-marker, boosting “enthusiasm, optimism and turnout” for Bishop with Monday night’s rally.

“The haters waste so much time trying to insult and impede the president that they fail to grasp the political currency he conveys in tight races like this,” said Conway.

The president took even more credit for Bishop’s win, writing in a victory lap on Twitter that Bishop was trailing and “asked me for help, [and] we changed his strategy together, and he ran a great race.”

Bishop’s embrace of the president — in the closing days of the campaign, he repeatedly decried the treatment Trump had received from Democrats and the news media and said he would go to Congress as a vocal Trump defender — also serves as a playbook for other Republicans.

“Republicans should be watching: Run with the president and win,” Conway said.

That could include vulnerable incumbents like GOP Sen. Thom Tillis of North Carolina, who is facing a spirited primary race from a self-funding opponent accusing him of insufficient loyalty to Trump, in addition to the challenge of seeking reelection in a swing state.

Republicans were quick to trumpet the success of their coordinated effort — from last-minute visits from Trump and Vice President Mike Pence, all the way down to the congressional leaders and the constellation of official and outside groups and super PACs — in pushing Bishop across the finish line.

That may not be replicable in November 2020 all the way down the ballot. But Trump’s robust campaign operation — which he continues to build as Democrats fight for their party’s nomination — will be formidable, despite the president’s low political standing compared to past incumbents.

“The White House, Republican leadership and all our Republican and conservative partners were there for us every step of the way because they all understood what was at stake in this election,” Bishop said in his victory speech Tuesday night.

For McCready, who campaigned for this House seat for 27 months — launching a campaign in 2017, suffering an apparent defeat in 2018 only to run again in 2019 when the previous election was voided amid credible allegations of ballot fraud — he sounded some of the same bipartisan notes that twice brought him close to winning a congressional seat Democrats haven’t held since the 1960s.

“We may not have won this campaign, but that does not mean we were wrong,” McCready said in his concession speech. “And as long as there are people who thrive off our division, there is still work to be done.”