Fourth update because something important changed: DOJ has now answered the challenge.

North Carolina starts mailing ballots September 4.

The court's temporary order still lets USPS build its new system, review envelopes and let states use the portal.

What USPS cannot do right now is reject ballots for failing the new federal requirements.

DOJ is asking the appeals court to restore that power immediately. It argues that allowing ballots to go out without the new checks would cause the government "immediate and irretrievable" consequences.

And DOJ's answer to ballots USPS rejects is striking:

"Any noncompliant mail can be corrected and then mailed."

That's the signal.

DOJ calls it irreparable harm if ballots are mailed without Trump's new federal checks. But if USPS stops those ballots, its answer is: fix them and mail them later.

With ballot mailing beginning this week, those are two very different standards for whose delay matters.