Trump didn't say that he was concerned about voter fraud. He said the election is rigged for him to lose. Why would anyone listen to a political candidate who said something like that?
That's like having the CEO of Coca-Cola stand up and say he has the best product in the world, but no stores are willing to carry it. Well, great -- so I guess I won't even bother looking for it!
Why? Because it’s the left that commits voter fraud. Jumping to your assumption ignores this and your analogy is ridiculous. The Clintons in particular and the Dems in general have a long history of cheating going back to Tammany Hall. There is no history of stores colluding against Coke.