While the National Popular Vote does not require a Constitutional amendment, it still fails to give representation to both the national population and state-by-state concerns. The most populated areas of the country would have an unequal (unfair) advantage. Potentially, it could create greater voter apathy.
More importantly, however, is that it would be nearly impossible to have all 50 states and Washington, D.C. convert to the National Popular Vote approach before a number of election cycles passed. In the intermediate elections (before the entire country uses NPV), vote suppression would be even greater than it is today. Voter turnout would most likely plummet with voters realizing their vote did not matter.
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