So your assumption would require not only the thousands of Democrats which would be required in the states in order to commit this voter fraud would ALL keep their mouths shut...AND that we Democrats are so much smarter than the Republicans that we can do all that and leave no trace.
It's either that, or...
...there's no massive voter fraud.
But of course since it's unthinkable that the Right is ever wrong about anything, and that the Democrats are the root of all evil, then it must be that the Dems are SUCCESSFULLY committing voter fraud on a scale of complexity never seen before by any conspiracy in human history...and keeping it all so very quiet among themselves. Riiiiiiight.