On November 7th, in Washington, D.C., after delivering a speech to the Campaign for the Fair Sentencing of Youth, Eric Holder grabbed his Blackberry in search of results from the Virginia elections. As the former Attorney General scrolled backward through a long e-mail thread, he quickly learned just how stunning a night it had been for the Democrats. He also understood that, after this triumph, it might be a little harder to keep his party focussed on gerrymandering.

“The system didn’t become more fair as a result of what happened last night,” Holder told me the next day. “The system appears to be more fair in spite of the reality that those Democratic candidates faced. The job that I have is to make sure people don’t become complacent.”

Holder has spent the past year tackling the once hopeless task of making redistricting sexy. He leads the National Democratic Redistricting Committee, and its charge is nothing less than saving the Party’s prospects for the next decade. Big donors need to be convinced that state legislative races matter as much as the Presidency; congressional leaders, desperate to retake the House in 2018, need to recognize that long-term down-ballot success is crucial to unlocking future majorities. These are not easy arguments to pursue with politicians who are narrowly focussed on their next election. It’s even harder when they believe that an electoral wave—one like last Tuesday’s—rather than sacrifice, compromise, and planning, will save them.

“Their professional lives are going to be a little less certain,” Holder said. “But Democrats can’t go through another decade like the decade we are in now. In another decade, Republicans could solidify this in such a way that, well, you’d be talking about such structural changes that I’m not sure we could overcome even when you get to 2031.”

Democrats slumbered through redistricting in 2010, but they’re awake now. Their snooze, however, coincided with an audacious Republican strategy called REDMAP, short for the Redistricting Majority Project. Republicans targeted control of state legislatures, with an eye toward dominating redistricting of state legislatures and U.S. House seats. They fought especially hard in battleground states that were likely to gain or lose a member of Congress in the decennial post-census reapportionment.

In 2008, Democrats held nearly sixty per cent of state legislative chambers. Now Republicans control almost seventy per cent. Democrats have not flipped a congressional seat blue all decade in ostensible swing states such as North Carolina, Michigan, Ohio, Pennsylvania, and Wisconsin. Those states are currently sending a total of forty-eight Republicans and twenty Democrats to D.C. During the Obama era, Democrats also bled nearly a thousand state legislative seats nationwide. They hold fewer than forty per cent of the lower-house seats in four of those five crucial purplish states. The exception is Michigan, where Democrats have gained more aggregate state House votes than Republicans in each of the last three statewide cycles, but can’t break past forty-two per cent of the seats.

These state legislative gerrymanders have proven so durable that Democrats need to elect governors simply to have a seat at the table when new maps are drawn in 2021. Virginia provided a first dry run, before a full slate of crucial governors’ races next year in Michigan, Pennsylvania, Wisconsin, Ohio, and Florida.

In speeches before multimillionaire donors and in countless e-mails seeking as little as five dollars from the grassroots, Holder contended that Democrats needed to elect Ralph Northam governor in Virginia, over the Republican Ed Gillespie, so that the Party could veto any extreme partisan maps drawn by a G.O.P. legislature after the 2020 census. The N.D.R.C. poured $1.2 million into Northam’s coffers, its biggest investment by far.

Since Gillespie is a longtime Washington lobbyist who designed the G.O.P.’s 2010 redistricting strategy, Northam’s victory was that much more satisfying. But then the gerrymandered House of Delegates—controlled 66–34 by the Republicans at the beginning of the night—suddenly appeared to be in play. Democrats have gained at least fifteen seats. If Republicans hang on to their leads in three districts awaiting recounts, they will eke out a 51–49 majority. “To have that kind of a swing on the gerrymandered map was breathtaking,” Holder said.

The G.O.P. gerrymander would make the difference: Northam carried Virginia by nine percentage points, and Democratic House of Delegates candidates statewide also outpolled Republicans by nine points—in other words, it required nearly a double-digit Democratic win to approach parity. “It’s a wave election just to get to fifty-fifty,” Holder said. “We can’t lose sight of that . . . With fair maps, with fair lines, you would have expected Democrats would’ve done far better than they did.”

For these reasons and more, Holder wants Democrats to guard against overconfidence. As he watched the Democratic gains in Virginia’s House of Delegates last week, however, he also wondered how a dramatic electoral upset might affect Supreme Court Justices weighing Gill v. Whitford, the crucial Wisconsin case that could lead to the first-ever constitutional standard to rein in partisan gerrymandering. That case is centered around the state-assembly districts that Republicans drew in 2011. Those lines proved so friendly to Republicans that, in 2012, Democratic assembly candidates earned a hundred and seventy-four thousand more votes than Republicans, but the G.O.P. won sixty of the ninety-nine seats.

In oral arguments last month, conservative Justices suggested that there is no need for the Court to involve itself with partisan gerrymandering, because voters are always capable of toppling even extreme lines at the ballot box. Paul Smith, representing the Wisconsin voters protesting the maps, vehemently disagreed. He told the Court that “this map is never going to flip over. The evidence is unequivocal that the Democrats would have to have an earthquake of unprecedented proportions to even have a chance to get up to fifty votes out of ninety-nine.”

Chief Justice John Roberts, however, reminded Smith that a lawyer made a similar argument to the Court a decade earlier, when partisan gerrymandering last appeared before the Justices. A few days later, the Democrats flipped Pennsylvania. “They won every single race,” Roberts said. “Predicting on the basis of the statistics that are before us has been a very hazardous enterprise.”

Holder recognized that the Virginia results might persuade conservatives on the Court—and newly hopeful Democrats—that wave elections can beat back gerrymanders. “My hope would be that there would be a level of sophistication there to look at what happened in Virginia and understand what really occurred, then to put it in context,” Holder said.

A big win provided new, if not unwelcome, challenges. “There’s another layer now to this job,” Holder said. “Democrats need to understand that this happened in spite of gerrymandered districts. I suspect the other side might point to Virginia and argue, ‘This shows that the whole question of gerrymandering is not a legitimate concern.’ And, in fact, it is. We can’t lose focus based on one night.”