What does the change in election results suggest about how American society has been altered because of Eckels' error?

The election change suggests that American society has pulled a complete 180 degree turn around.  In the beginning of the story, the reader is told that Keith has been elected President of the United States.  We are told that he will make a great President.  

"Thank God Keith won. He'll make a fine  President of the United States." 

We are also told that the people are glad that Deutscher lost.  Apparently that guy would have turned...

The election change suggests that American society has pulled a complete 180 degree turn around.  In the beginning of the story, the reader is told that Keith has been elected President of the United States.  We are told that he will make a great President.  

"Thank God Keith won. He'll make a fine  President of the United States." 

We are also told that the people are glad that Deutscher lost.  Apparently that guy would have turned the government into a dictatorship that is anti-everything.  

"There's an anti everything man for you, a militarist, anti­-Christ, anti-human, anti-­intellectual."

The brief exchange about the two candidates is meant to inform the reader that the two men stand for things that are at polar opposite ends of the spectrum.  They are in no way related or alike.  

At the end of the story, it is revealed that Deutscher won the election.  What this means is that Eckels's tiny, little, minuscule change to the past has not resulted in a small change in the present.  The death of that single butterfly has changed everything.  This story didn't coin the phrase "butterfly effect," but the story does a wonderful job illustrating the principle of the butterfly effect.