A triple-tie that results in President Pelosi on Jan 20 is not impossible -- plus cancelling elections
It is possible if, among the swing states, Trump wins Florida, Pennsylvania, North Carolina and the Nebraska 2nd (Omaha), while Biden wins Michigan, Arizona and Wisconsin. This is not one of the most likely scenarios, because Arizona and Wisconsin are currently more on Trump's side than Biden's, but it's possible.
This would result in a tie, or rather, no candidate getting a majority. That means the newly elected 117th House picks between them, and the Senate picks the VP, in what is called a Contingent Election.
The House votes by state, not by member. 26 state delegations are needed to win. Right now Republicans control 26 house delegations, and 2 are tied, and 22 are Democratic. That House would elect Trump. But if any weakly red delegation such as Florida or Wisconsin were to flip blue in the new congress, the house would deadlock.
It doesn't say in the constitution how a state decides its vote -- the decision is to be made immediately, though. One presumes the members of the state delegation themselves hold a sub vote -- more on that below.
If there is a deadlock, the new VP becomes acting President until the House comes to a decision. Who is the new VP? Well, that's chosen by the Senate, so today, it would be Pence. But it's not entirely out of the question that the Democrats could pick up 3 Senate seats, and there would be a tie there too! Without 51 Senate votes, there would be no VP -- no specific process is specified for how to select one in this tie.
The 20th amendment then says that "Congress" can set rules for how to choose a President if there's no VP. I haven't found a lot of details on that, particularly on how a deadlocked congress would do that.
One article I read suggested the order of succession would be used, resulting in President Pelosi. It is quite unclear who would become VP. Next in line is the President Pro Tempore of the Senate, who would not exist with the deadlock either. After that you get cabinet members like the Secretary of State, though a new one could not be confirmed by a tied Senate with no VP.
Another odd option opens if the lack of majority comes from a 3rd party candidate gets any electoral votes. Then than 3rd place spoiler could be a compromise candidate for a deadlocked congress to choose. I wrote in 2016 how that could have happened to Evan McMullin.
As I said, it's not written down where I could find it that the states decide their vote by a vote of members. It's not written down what the evenly split delegations do (probably abstain.) It's also possible that a house member might break from party. What if your district went heavily for Biden, and your vote made the difference in electing Trump?
Now, all of this is unlikely for another reason. The pattern of states to get a tie in the college is not an expected one, since it has Trump win the slightly more blue swing states while Biden wins the slightly more red ones. It also needs enough of a "blue wave" to flip the house delegation of a red state, and for the Democrats to gain 3 Senators. Though without that gain, Pence is VP and then acting President, which Democrats could consider an improvement.
It's also possible that the Republicans could have a majority of states in the House as they do now, but the Democrats somehow got 51 Senators. This would result in President Trump and the Democrat VP. Also remotely possible is the Democrat VP becoming President with a deadlocked house and a Democratic Senate.
So it's not going to happen. But it's amusing to imagine.
There has been some suggestion of elections being cancelled in some states due to the virus. Ohio already delayed its primary.
This also is unlikely, since every state currently has some form of vote by mail. 2/3rds let anybody do it. 1/3rd need an excuse, but obviously there is an excuse.
In fact, the important swing states -- AZ, WI, MI, PA, NC and FL as well as OH, have republican controlled legislatures, but all but Florida, Arizona and Ohio have Democratic governors. Biden has to win 38 votes from those states, and if any get taken out, it could hurt him. It could also hurt Trump, but again, he probably wins the contingent election.
The "good" news? If Sars-COV2 is that bad in November, and the stock market is down with it, the election is probably not so close that this can make a difference. It will be Biden's to walk away with.