Of course you should hold him accountable. Vote against him. What does that have to do with Twitter "fact checking" something that isn't even a statement of fact? Do you think they'll start fact checking things like statements of fact about the gender pay gap, perhaps the most debunked concept in all of economics?

If you're going to autistically parse the President's tweet, then I will gladly point you towards the word "substantial" in the President's tweet. How do you intend to gauge the President's internal thoughts regarding what he believes would be a "substantial" amount of fraud? He might feel a single bad vote is substantial.