The Democrats stole the election of 1960 and Nixon allowed it to happen because he feared it would tear the country apart if he revealed the Democrats had stolen the election.
Don't count on Trump being like Nixon.
If the Democrats steal this election, Trump will do everything in his power to let people know and he will file lawsuits and otherwise do whatever he feels necessary to make sure the election does not get stolen.
Democrats know this and are already prepared, saying that Trump "would not honor the results of an election if he lost." They even had a couple of retired generals tell the military to overthrow Trump in a coup d'etat if the Democrats steal the election and Trump refuses to acknowledge it.
If Trump supporters believe the Democrats stole the election, they will come out in force and we will then see real violence between Democrats and Trump supporters.