It seems the 'plan', such as it is, is to go off early figures and try and claim he's won before the counts are finished. The Republican vote apparently mostly happens on the election day, whereas Democrats are more likely to vote by mail than Republicans, and the mail ballots mostly won't get counted until the next day/ week.
The problem for him is not only that it's a load of bollocks and he can't just claim victory and everything will stop then and there, but there have already been getting on for 100 million early votes as well, so it's highly doubtful he'll appear to be ahead in any of the swing states he needs. The most likely effect is going to be getting his dickhead supporters riled up than actually being able to steal the election.