If Republicans want to change the law to allow this, they will need to go through the Democrat held House first.
Also, the 20th Amendment states “the terms of the President and the Vice President shall end at noon on the 20th day of January.” So even if the election were somehow canceled, Trump and Mike Pence’s terms would still expire as scheduled. Power would then very likely shift to whoever held the next highest level of office... which would be Speaker of the House; Nancy Pelosi.
