At least for Federal elections. We need a uniform, nationwide system of Federal voter registration and elections run, funded, and inspected on the Federal level.
It wouldn't take a Constitutional amendment.
Article I, Section 4, first paragraph:
The Times, Places and Manner of holding Elections for Senators and Representatives shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Place of chusing Senators.
Unless I missed some big catch in the Constitution, that leaves the door wide open for Congress to establish national voter registration by regular legislation -- at least for election of Senators and Representatives.
It would seem eminently sensible to use the same system for popular vote for President, but I'm not sure Congress can mandate that. That's because (again, unless I missed it) there's nothing in the Constitution that even requires each state to pick its Electoral College Electors by popular vote. The last word seems to be Article II, Section 1, second paragraph:
Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress; but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector.
I suppose a state legislature could even chose the Electors itself every four years, or delegate the choosing of Electors to the Federalist Society, or to Move On. I don't see anything in the Constitution that even requires there be a nationwide popular vote related to picking a President, even indirectly by statewide election of Electors.
I haven't reviewed the legislation being promoted by National Popular Vote
http://nationalpopularvote.com/
and I haven't gotten a copy, much less read, their 600-plus page book on their program. Has anyone done my homework for me? Does the National Popular Vote uniform bill that has been passed by four states and 21 of the 99 state legislative chambers (Nebraska has a one-chamber legislature) address these concerns? Specifically, does it call for uniform national voter registration procedures, and does it require all states, or at least all states that pass the bill, to hold statewide popular votes for President?
Don't tell the Republicans, but it seems to me that if the National Popular Vote movement passes, it pretty well requires that voter registration and elections (at least Presidential elections) have uniform rules. That would take vote suppression pretty much out of the hands of Secretaries of State like Katherine Harris and Ken Blackwell. We'd need somebody on the Federal level to run elections. That sounds like a cabinet-level position. I can perfectly well imagine a president like George W. Bush trying to appoint somebody like Alberto Gonzales or Karl Rove to such a position, but since that person would also be running elections to the House and Senate, I'd hope Congress would refuse to confirm anyone who wasn't squeaky-clean. Maybe the national election commissioner should be removable by a one third minority of Congress.
If I didn't have a board examination to study for, I might find the energy to learn enough to answer my own questions. As it is, I have an excuse. I'll try to rattle the cage of the folks at National Popular Vote and see if they've already taken care of this worry.
UPDATE:
It seems the National Popular Vote legislation pretty much leaves it to each state to be honest about how they register voters and report votes. That's more or less where we stand now, but right now one state's finagling can only affect that state's electoral votes. It seems to me that enacting National Popular Vote would leave open a distant possibility that one state might register 200 million fictitious voters and report their votes, swamping the 100 million real votes from other states. I suppose there is precedent for Federal courts stepping into disputes about how a state counts its votes, but the example that comes to mind for me -- Bush v Gore in Florida in 2000 -- still gives me heartburn.