The dead-enders have several theories.
1. When Congress counts the electoral votes on Dec. 14, they refuse to count certain states because of "irregularities." However, there's no constitutional mechanism for this. Congress is not a court of law, and no evidence of voter fraud may be presented. You would also need a majority to go along with this.
2. A case is brought to the Supreme Court, which nullifies the election. Again, there's no constitutional mechanism for this. Also, the Supreme Court doesn't hear evidence; it rules on questions of law when the evidence is not in dispute. That's not the case here when not everyone agrees that there was fraud in the first place.
3. Insurrection. This would require coordination and logistical planning. We would know if this was happening. Trump would be taking to the military and organizing a coup. The problem with this is it would be blatantly unconstitutional; in fact, it would render the Constitution null and void.
4. I'm sure some people think that on January 20, Chief Justice Roberts can simply decide to swear Trump in instead of Biden and settle it that way.