Summarizing an interesting analysis of the consequences of failing to hold the November elections:

The Founders considered the possibility that the Electoral College would fail to return presidential and vice-presidential appointees (note that these are actually two separate decisions by the body) prior to the end-of-term for the current office holders.

The outcome also reflects the fact that Congressional terms end on January 3, while the Executive Branch terms end later (typically around January 20).

1. If no elections are held, the Electoral College will fail to select either a President or Vice President.
2. On January 3, the entire House of Representatives loses office, while the Senate reconvenes with only those whose terms are held over from prior elections. Since the bulk of the expiring Senators are Republicans, the sitting Senate will be controlled by the Democrats
3. When the President and Vice President leave office around January 20th, nominally the Speaker of the House becomes President. But the House is not convened, so the fallback is to the Senate Pro Tem, which – since the Senate will be controlled by the Democrats – is going to be Chuck Schumer.

So as of January 20th, Chuck Schumer becomes President of the United States. Unless he doesn’t want to be President, and props up the selection of a Pro Tem who does.