Here is a horrible idea. At least if you believe in the sovereignty of the States. The author has the right conclusion, but for the wrong reasons. States elect the President, not voters, per se. This was intentional. Direct election of the President eliminates another vestige of sovereignty from the individual States and strengthens a large central government. It makes the more populous states more important in the election process and reduces the influence of smaller states. Right now, Wisconsin (population of about 5 million) is seen as a more important state in the presidential election than, say New York (population of nearly 20 million). New York is a pretty reliable Democrat win, but Wisconsin is needed to win the election. Under the national Popular Vote (NPV) plan, Wisconsin becomes irrelevant while New York, California, Texas, Florida become the major prizes.
If the States are sovereign and equal, NPV is a horrible idea.