Strategically speaking, we urge President Trump to declare the insurrection before the election, because this would allow him to challenge the Electoral College votes from states which are supporting open rebellion against the United States (for all the reasons noted above). Even if Trump declares the insurrection just one day before the election, this grants him a basis from which he may challenge the Electoral College votes from insurrectionist states like California.
It also grants Trump the opportunity to arrest all the corrupt, left-wing officials the day after the election, shutting down their criminal attempts to counterfeit ballots after the fact that try to “win” by cheating in the weeks following the election itself. Trump can largely shut down that effort by simply declaring an insurrection and arresting all these treasonous actors the day after the election. They cannot counterfeit more ballots, after all, if they’re sitting in jail.
This action would, of course, cause the radical Left to ignite an attempted nationwide kinetic war against the government, but at that point Trump is free to issue escalated engagement orders for federal law enforcement while even bringing in the U.S. military to halt all domestic enemies of the United States who are engaged in acts of treason or warfare against America (deploying the military to defeat domestic enemies of America does not violate Posse Comitatus).