In “How Democracies Die,” Levitsky and Ziblatt write that “if one thing is clear from studying breakdowns through history, it’s that extreme polarization can kill democracies.” Page 9.
The presidential selection system not only does not temper polarization, it highly motivates candidates to adopt polarizing positions. The reason is that swing states are typically concentrated regionally. As candidates focus almost exclusively on winning these states, they appeal to local issues likely to inflame two evenly balanced constituencies (which balance is the definition of a swing state). The moderating influence of the great majority of Americans is irrelevant under this system.