"We really ought to be able to come up with some way to coordinate things and make sure that each legally registered voter gets 1 vote and cant double up from precinct to precinct or state to state. "
Try the purple thumb. Worked great in Afganistan. Cheap, too.
Unfortunately, this would not stop snowbirds from voting in New York or New Jersey by absentee ballot and in Florida in person. Someone posted an estimate of 46,000 overvotes because of this. Given the Dems' penchant for voter fraud, I would be willing to bet that there are a lot more than that who are voting several times in different states by absentee ballot.
As much as I distrust giving more power and authority to the Federal Government, I can not come up with any solution other than a national voter registration.