A voter registration failure in Virginia shows the real risk to fair elections.

The state’s online voter registration system crashed on Monday, the final day for Virginians to register to vote in the November 8 election. The state registrar said an unknown number of people were unable to register by the midnight cutoff, but the Stafford County registrar estimated to The Washington Post that “tens of thousands” of people were shut out. “It got inundated to the point where it was useless for everyone,” he said.

This is how elections are compromised. It’s not Hillary Clinton and the media somehow “rigging” it. It’s not Democratic voters rising from the dead. It’s when fallible systems—both human and electronic—fail to perform as expected. And that is almost certain to happen, to some degree, on election day. As Lauren Smiley writes in the latest issue of The New Republic,

[T]he biggest threat to the sanctity of the vote is the voting machines themselves. Like so much of America’s crumbling infrastructure, the systems we rely on to tabulate our votes fairly and accurately are in dire need of an overhaul. In thousands of precincts, the outcome of the election rides on equipment that’s outdated, prone to errors, and difficult or impossible to repair.

The Lawyers’ Committee for Civil Rights Under Law has already filed a federal lawsuit over the Virginia incident, arguing that the failed registrants’ constitutional rights were violated and calling for a three-day extension of the deadline. (Citing state law, Governor Terry McAuliffe’s office and state officials say they don’t have the power to do so.) Election day promises to be a whole lot messier. Machines will crash, irregularities will be reported. But when they do, the proper response from the American public will not be to parrot whatever conspiracy theory Donald Trump cooks up, but to demand that elected officials—starting with the incoming president—fix our country’s electoral infrastructure.