Psychologists call this motivated reasoning, and it means that once people have thrown their support behind Trump or Clinton, they will tend to downplay or ignore things that paint their candidate in a bad light.
Check out this amazing comparison site put up by WSJ - Blue Feed, Red Feed. It highlights what a self professed liberal and conservative actually see on facbeook based on its algorithms. If one is limiting their exposure to contrarian ideas, they have the ability to increasingly live in a circlejerk.
Now, a highly polarized nation (by which I mean the actual public and not the politics) can lead to a state of disarray. However, what America is facing right now is polarized politics. At least we feel that we are highly polarized. Vox highlights a Pew report that suggests that political polarization is at a global maximum.
It turns out that the American public is not that polarized. What they are though is less open to changing their stance. The verysame study suggests that the American public have increasing ideological consistency. In other words, we are less open to changing our opinion about stuff.
What might be the nudge needed for both sides to open up to each other's ideas for their merits? What might bring about the utopian compromise that powered America? What might be the case that will actually unite the cause for America? It is certainly not the current Presidential candidates, apparently.