The equipment that states have to conduct in-person elections won’t work for mail-in elections. The scanners many states have to count ballots in each polling places can’t handle counting ballots en masse from the whole county or state. The kind of scanner that can do that heavy work costs $500,000 to $1 million, said Wendy Underhill, an elections expert with the nonpartisan National Conference of State Legislatures.

Also, states can’t just mail out the ballots they already have printed. They have to design ballots that can be folded into an envelope. They also need to print instructions for how to fill it out and send it back. And they need to design the ballot to work with the Postal Service, Underhill said. “So instead of one piece of paper with a ballot, you have several pieces of paper that need to be prepared,” she said…

The staffing must change with a by-mail election, too. To run a day-of election, states probably need several thousand poll workers willing to come in for 12-14 hours on a single day. For a by-mail election, states might need a fraction of those staffers, but they’ll need people who can work for weeks before the election helping get it set up and then weeks afterward helping count ballots.