The great political scientist V.O. Key theorized that certain presidential elections could be classified as "Critical Elections" because they changed the political calculus for years thereafter. The classic example is Barry Goldwater's 1964 run against Democrat Lyndon Baines Johnson, where Goldwater lost but in doing so laid the foundation for the Republican Party's rise to power for years thereafter. Ever since, political scientists have wondered when we might see the next such critical election. The true test is a sustained change, seen through the rear view mirror of history. A McCain win tonight likely won't change the current calculus. But a big Obama win could put that question back in play for the first time in 44 years. For clues, watch not just for changes in red states and blue states, but for changes in key voting demographics - especially higher income, higher educated white males.