Yes, the number is electoral votes available just goes down. I suppose you could have only one state voting and have it decide the Presidential election? But you wouldn’t have much of a Congress. Every rep is elected every two years, so the house would be emptied of every non-voting state. The senate would loose 1/3 of its members. Without full elections, we really don’t have a government.

Of course they could have elections but leave the President off the ballot, but I think that would be harder to sell. Even if you somehow felt Trump could have a third, unconditional term, he still has to be elected to that term. How you could have an election but not for President I can’t even imagine.