Although the Virginia governorship was Tuesday's marquee race, the Virginia House of Delegates produced the day's most surprising result. Democrats picked up at least 15 seats and reduced a 66 to 34 Republican advantage to, at most, 51 to 49. A gerrymandered chamber thought to be safely Republican suddenly became a toss-up — and may yet flip to Democratic control after all the recounts are completed.
This unexpected outcome raises the question: Can gerrymandering really be such a problem if a party's legislative edge can virtually disappear overnight? This question is especially important at present, as the Supreme Court mulls over Gill vs. Whitford, a potentially historic case about redistricting in Wisconsin.
The question also has a clear answer: Of course gerrymandering is deeply troublesome even if it can be overcome, at least temporarily, by a wave election.
Consider the following facts about the Virginia House of Delegates: In three previous elections (2011, 2013 and 2015), Republicans won 66 or 67 out of 100 seats. Republicans maintained this supermajority even though Democrats narrowly won every statewide race over this period. To secure (roughly) half of the House seats on Tuesday, Democrats had to earn well over 50% of the statewide House vote. This was Democrats' best showing in more than 30 years. Had Republicans done as well, they would have won far more than 50 seats: close to 70, in fact.
The upshot of these statistics is that gerrymandering works. The Virginia district plan operated exactly as intended in prior elections, returning overwhelming Republican majorities even when voters slightly preferred Democratic statewide candidates. And while a Democratic tsunami hit Virginia on Tuesday, if it recedes even modestly, the map will revert to massively favoring Republicans.
A second crucial point is that, although no one can predict a wave with certainty, a plan's performance if a wave arrives can be accurately forecast. In the 2016 presidential election, Hillary Clinton won 17 Virginia districts represented by Republican incumbents. So it was apparent ahead of time that if Democratic candidates could match her showing, they would flip a large number of seats. And it was unsurprising that when Democrats substantially improved on her numbers, they prevailed in the bulk of these vulnerable districts. In fact, 14 of Democrats' 15 pickups (so far) were in districts previously won by Clinton.
A final point is that not all maps are equally at risk if a Virginia-sized wave materializes. Take the Wisconsin state house plan at issue in Whitford. Its authors were not quite as greedy as those who drew the Virginia map. They were content for Republicans to win three-fifths (rather than two-thirds) of the seats in normal conditions. This somewhat less ambitious target let them sprinkle more Republican voters into each Republican district, yielding bigger margins and more leeway in the event of a Democratic groundswell.
Consequently, there are only three Wisconsin districts (out of 99) won by Clinton but represented by Republicans. If Wisconsin Democrats do as well in 2018 as their Virginia counterparts did in 2017, they will likely flip just four seats. For Democrats to win a majority of the Wisconsin Assembly, they would need a further five-point boost — a 100-year flood rather than an ordinary wave.
It's true, then, that with enough wind at its back, it's always possible for a party to earn a legislative majority. But "enough" is a relative term. A clever gerrymander can set the bar almost impossibly high, condemning a party to minority status in all but the most extreme circumstances.
Nicholas Stephanopoulos is professor of law at the University of Chicago, where he specializes in election law. He represents the plaintiffs in Gill vs. Whitford.