Susan,
A good place to start would be to have your students read the statement
Daniel Patrick Moynihan (D-NY) gave on the senate floor back in 1979.
Also, when discussing the possibility of another election in which the candidate with the popular vote loses the election, you might want to have the class debate a point not mentioned in Moynihan's statement, but brought up by
Walter Dellinger (U.S. Solicitor General under Bill Clinton):
[W]e simply do not and cannot know who would have won a national popular-vote contest had one been held. In such a case, both candidates would have run fundamentally different campaigns, emphasizing different issues and appearing frequently in states like California, New York, and Texas. Who can know how people in those states would have responded had they been as informed by exposure to the candidates and their ads as citizens in Wisconsin and Ohio? One cannot persuasively impeach the electoral vote with a national popular-vote number that was wholly irrelevant to the campaign that was actually run. The hypothetical question of who would have won a national popular-vote contest if one had been held is thus completely unanswerable.
