Or just have him arrested for treason, he is attempting to give aid to Trump, who tried to use fake electors in an attempt to steal the presidency. I would list anyone who tries to steal the presidency as an enemy of the state.
He can sit on those charges until a judge gives conviction. (I doubt there would be bail on a treason charge, and the only out if convicted would be a federal pardon)
That's a fair bit more serious, and much harder to prove. To convict this guy of treason, you would also need to convict Trump of treason, and both would need to be proven beyond reasonable doubt - ie it is more than 99% certainly true.
Defamation is a civil claim, which means it is decided on the balance of probabilities. This means whichever side tips the argument past 50%.