He should have run again as a Libertarian, he would have a much better shot, he won't do anything against Trump but lose money.
Better shot? At winning the presidency? Or better shot at gaining the Libertarian nomination? He clearly didn't get the Libertarian nomination last round ... and won't get it this time. And yeah... even if he does get the nomination? He has even less a chance of becoming president at that point.
Not saying he has a snowball's chance of surviving a Tsar Bomba blast of getting the Republican nomination ... barring a Trump impeachment but... at least he can help to change the party platform come official primary season starts.