Updated at 3:06 p.m. on November 3, 2020.
As polling places closed on November 6, 2018, the expected “blue wave” looked more like a ripple. Not only had some of the highest-profile Democratic candidates lost, but the party’s gains in the House and the Senate looked smaller than anticipated.
The wave, it turned out, simply hadn’t crested yet. Over the ensuing weeks, as more ballots were counted, Democrats kept winning races—eventually netting 41 House seats. In Arizona, the Republican Martha McSally conceded the Senate race to the Democrat Kyrsten Sinema, who picked up more than 70,000 votes in post–Election Day counting. Democrats narrowed deficits in races in Florida and Georgia too. Republicans were stunned.
“California just defies logic to me,” then-Speaker Paul Ryan said in late November. “We were only down 26 seats the night of the election and three weeks later, we lost basically every contested California race.”
This sort of late-breaking Democratic vote is the new, though still underappreciated, normal in national elections. Americans have become accustomed to knowing who won our elections promptly, but there are many legitimate votes that are not counted immediately every election year. For reasons that are not totally understood by election observers, these votes tend to be heavily Democratic, leading results to tilt toward Democrats as more of them are counted, in what has become known as the “blue shift.” In most cases, the blue shift is relatively inconsequential, changing final vote counts but not results. But in others, as in 2018, it can materially change the outcome.