Historian Julian Zelizer explores this question at CNN.com. Here is a taste:
If Richard Nixon taught the baby boomers that they could never fully trust a president, Trump is erasing any expectation whatsoever that the president should aim to heal and lift the dignity of the Republic.
Most striking has been the fact that he abandoned any sense that a president should strive to achieve unity. He is at war with almost everyone. One of his most consistent characteristics has been his willingness and eagerness to divide. Since his campaign, he has introduced Americans to a new enemy on a weekly basis.
Read the entire piece here.