Four recent special elections in Republican-held House districts, including Tuesday’s showdown in the northern Atlanta suburbs, have left both parties facing the same ambiguous equation they confronted as 2017 began.

Significantly improved Democratic performance in all four contests has provided evidence that enough voters are uneasy about Donald Trump’s turbulent presidency to give Democrats a competitive chance of recapturing the House of Representatives next year. But the GOP wins despite those Democratic gains have shown that enough ordinarily Republican-leaning voters are sticking with their party to give it a plausible chance of holding its majority.

This dynamic points to the sensible conclusion that control of the House in November 2018 will turn on events that have not happened yet—which is why special elections historically have had such limited value in predicting the next general election.

The Republican sweep of these contests—in Kansas, Montana, Georgia, and South Carolina, where Trump tapped House members to join his Cabinet—does have some tangible consequences. It has left Democrats frustrated and divided once again between centrists and Bernie Sanders-style progressives. (The latter group accused the party’s Georgia nominee, Jon Ossoff, of running a bland and insufficiently populist campaign.) For Republicans, the wins—especially Karen Handel’s victory over Ossoff this week—will help calm the nerves of incumbents, donors, and activists frazzled by Trump’s volatile first months.

“This is an important race in terms of controlling the narrative of the next six months,” said Tom Davis, the former Virginia Republican congressman who served as chair of the National Republican Congressional Committee. “That goes to who retires, how you recruit people, and where the transactional [political donation] money goes.”

But, as Davis quickly added, while the GOP sweep may change “the narrative” in Washington “it doesn’t change the facts.” By that he means Republicans will likely face a tough environment next year. While the GOP held all four seats, Democrats narrowed the margin significantly from last fall’s election in each district. Compared with November’s results, the GOP margins of victory declined from nearly 16 points to 6 in Montana, 23 points to less than 4 in Georgia, 21 points to 3 in South Carolina, and 31 to about 7 in Kansas. Shifts of that magnitude next year would topple many House Republicans holding more marginal seats than these four.

In part, the Democratic improvement is explained by the fact that this year’s contests, unlike last fall’s, were open races without an incumbent. But such large shifts could not occur unless Democrats in these places were energized to vote and at least some independents were shifting away from Republicans. Unease about Trump fuels both of those movements.

Attitudes toward Trump still loom as the key factor in next year’s congressional election. In each of the past three midterms, 82 percent to 84 percent of voters who disapproved of the sitting president at the time voted against his party’s candidates in House elections, according to exit polls. Between 84 percent and 87 percent of those who approved voted for the candidates of the president’s party. Recent Quinnipiac University polling has found that pattern even intensifying, with 93 percent of those who approve of Trump’s performance indicating they prefer GOP control of the House, and 86 percent of those who disapprove saying they want Democrats in control. The clear danger for Republicans is that, nationally, only about four in 10 voters (or less) approve of Trump’s performance.

However, that threat was muffled in the four solidly Republican-leaning districts that recently held elections, because Trump was much more popular there than he is nationally. Both public and private polling in the Georgia district, for instance, found that about half of voters approved of him. Trump’s relative local strength compelled Ossoff, as one adviser told me, to “serve two masters.” He needed to activate Democratic voters with a targeted message of resistance to Trump through mail and digital advertising. But Ossoff concluded he could not stress opposition to the president in radio and television ads that were aimed at swing voters. At least in these Atlanta suburbs, those voters still “want to give this guy a chance,” the adviser said.

That instinct may be surprising, given how the Georgia district is crowded with the well-educated, suburban white voters with whom Trump has struggled. But Handel’s victory offered another reminder that the Southern suburbs are different than their counterparts elsewhere—likely because fewer of their residents are social liberals. In both the 2014 Senate and 2016 presidential races, for example, Democrats won less than three in 10 college-educated whites in Georgia, far below their national showings.

One lesson of Handel’s win is that geography, not just demography, counts and that Democrats can’t assume white Southern suburbanites will vote for them even if they are ambivalent about Trump. To recapture the House, Democrats next year likely will need to maximize their gains in places like the suburbs of Philadelphia, Los Angeles, and Northern Virginia, where culturally liberal views are more predominant and Trump’s standing more tenuous. (Democratic victories this November in governor’s races in New Jersey and Virginia, two states where recent polls put Trump’s disapproval rating at 60 percent or more, would highlight those opportunities.) But the failure in the Atlanta suburbs also suggests that Democrats are unlikely to retake the House without recapturing at least some blue-collar places, such as upstate New York, in otherwise Democratic-leaning states.

On both fronts, Democrats will need better answers to the GOP’s most effective weapon in Georgia. Neither entirely embracing nor repudiating Trump, Handel effectively steered the election more into a referendum on whether voters wanted Democrat Nancy Pelosi as House speaker. To fully capitalize on Trump’s vulnerabilities in 2018, Democrats will need a message and agenda that fixes more of their own.