It is! It's happening right now in NY and CA, which (being big, lazy, and mostly single-party) count their ballots like mollases. Biden's lead there has been steadily and inexorably climbing. And this despite the fact that they are neither swing states nor Virginia.

Can I flip the question around: can you show me a state with late mail ballot counting that is not trending toward Biden? The only exception I can think of is AZ over the past few days, but they're processing primarily provisionals in red counties at this point. The blue counties are done.

Edit: or alternatively, why is Arizona not evidence of fraud by Trump, given that it counted up very rapidly to Biden, leveled off when the early vote was complete, and then began processing different ballots that skewed differently. CLEARLY Trump is cheating with those provisionals, right?

The whole thesis is just silly. Different counties count at different rates. Different populations vote by different mechanisms, and the reported vote over time is an essentially random walk within that space. There's no mechanism by which you'd expect a consistent rate of margin growth. It doesn't even make sense.

Because smaller rural districts finish counting early, leaving only the heavily blue urban districts towards the end

> Why is this not happening in non-swing states other than Virginia?

On what basis do you say its not?

Mail ballots come from different counties with highly different demographics. You get massive Biden support in one city and massive Trump support in another rural county - it's not surprising at all. There's also differences in when the ballots arrived: some states could process ballots ahead of time so the late counted ones are only those that arrived late and may be more or less D/R leaning. And different states have different voter registration policies; that's why Arizona has had relatively good Trump performance on the later counts since there are a large number of Republican voters using vote-by-mail and there always have been in Arizona. There is boundless discussion of the specifics of this on twitter, etc. I don't think swing state/non-swing state is a useful categorization here. Just look at the where the ballots are coming from directly.

> Why is this not happening in non-swing states other than Virginia? And why does Biden's luck improve over time when _only_ mail in ballots are counted?

Cause voting is not luck based. Democrats are more likely to vote by mail. Partly because of covid, which they are more likely to believe is an issues. Plus, Trump and republicans discouraged mail voting and claimed it is fraudulent long before election. They did also tried to stop the mail counting and slow down post.

So, republicans were less likely to trust mail and more likely to vote in person.

Because Trump told all his base to NOT vote by mail.