The second presidential debate, taking a town-hall format, was originally scheduled for Thursday. Now Biden and Trump are participating in separate town halls. 

So what happened?

Trump disclosed on Twitter on Oct. 2 that he tested positive for COVID-19.

Six days later, the nonpartisan Commission on Presidential Debates announced the second debate in Miami would be virtual. It would maintain its town hall format, but unlike the first debate, the candidates would participate remotely from separate locations.

Biden agreed. Trump did not, telling Fox News moments after the announcement, “I’m not going to waste my time” on a virtual format.

With the president out, the Biden campaign signed on to an ABC News Town Hall. 

The Trump campaign, hours after saying Trump would host a rally on Oct. 15 instead of debating, then said it would participate in the second debate if it was pushed back a week and the final scheduled debate also was pushed back a week.

But the Biden campaign quickly shot down the idea of rearranging the dates, saying they were agreed to back in June.

So Trump made plans to appear in a NBC town hall in Miami, taking place at the same time as Biden's ABC News town hall.

Amid the back-and-forth between the campaigns, the Commission on Presidential Debates officially canceled the second debate in a statement last Thursday saying, “It is now apparent there will be no debate on October 15.”

Both candidates have agreed to participate in the third and final debate, which is scheduled for Oct. 22.

The live, 90-minute special airs on ABC Television Network at 8 p.m. ET/5 p.m. PT.

A half-hour post-event show featuring the ABC News political team for more context and analysis will follow the town hall portion and is also available on streaming. 

Biden and Trump will both face voters -- albeit not in the way envisioned by the debate commission or really any actual voters.

But however the collective audience sorts through an unusual evening, with Biden at an 8 p.m. ET ABC News forum in Philadelphia, and Trump at a competing event in Miami on NBC, voters are voting -- lots of them.

Records for this far out from Election Day are being set virtually by the hour and in virtually every state. Nationwide, more than 16 million ballots have already been cast, nearly five times the number logged at a similar point in 2016, according to records compiled by the most prominent authority on early voting, Michael McDonald of the University of Florida.

In Georgia, more than 537,000 mail ballots have already been accepted and returned, compared to some 200,000 in all of 2016. The start of in-person voting there brought hours-long lines this week; there have been similar scenes in Texas, where more than half a million voters showed up on the first day available to vote.

Nine states are already above 20% of their total 2016 turnout -- Election Day votes included -- with nearly three weeks left to vote. In-person voting starts in another key battleground -- North Carolina -- on Thursday.

It's too soon to extrapolate particular outcomes out of the interest in voters casting ballots early. Polls indicate a huge pre-Election-Day edge for Biden, and a sizeable Trump advantage among those who plan to vote on Nov. 3 itself.

Regardless, for all the noise around election integrity and distaste for politics generally, votes are pouring in. Biden and Trump are engaging with voters who have not only mostly made up their minds, but are acting on it every minute of the next 19 days.

-ABC News Political Director Rick Klein