From David Wasserman at The Cook Political Report:

The real danger is a perfect catastrophe of administrative overload, postal delays and voter error that could lead to millions of absentee ballots not counting. And this year, unlike the past, those ballots are likely to be overwhelmingly Democratic.

The problem for Democrats? Absentee ballots are rejected at higher rates than those cast in person. And academic studies have shown that younger voters and voters of color, some of Democrats’ most reliable voters, are much more likely to cast mail ballots that are rejected and less likely to take steps to “cure” their ballots if election officials flag them for signature problems.

There’s a relatively low risk of a meltdown in states accustomed to processing large quantities of mail ballots, such as Colorado, Oregon and Washington (where all elections have been conducted by mail for years) along with California, Florida and Arizona. But many of the highest-stakes Electoral College states face steep logistical curves as they rush to adapt to the COVID era: in 2018, mail-in votes were just six percent of all votes cast in Wisconsin and Georgia, four percent in Pennsylvania and three percent in North Carolina.

Growing fears over rejection rates could prompt Democrats to renew their focus on emphasizing in-person early voting as a means for those at lower health risk to relieve the burden on states’ strained mail and Election Day infrastructure. But early in-person voting isn’t available in some states, and there’s no guarantee lines to vote early would be less crowded than voting on Election Day.

“If I were advising someone at lower health risk, I would say think about early in person voting,” says Stewart of MIT. “But go early in the process and don’t wait until the last minute.”

I have been a strong proponent of the view that in-person voting is going to remain critical this fall. I am concerned that, with all the pressures state and local election officials face, they will neglect investing the efforts and resources needed to ensure a robust in-person option for voters this fall.