White supremacists are at one extreme of white identity. Social scientists developed a measure of white identity and they found that support for Donald Trump is strongly correlated with the degree of white identity. His support ranges from white supremacists at the high end of the scale to a much larger group of Americans with moderate scores on the white identity scale. White identity scores are also correlated with other factors such as immigration and political party affiliation. It is much stronger among registered Republicans. That process began with Richard Nixon's Southern Strategy which capitalized on Lyndon Johnson's civil rights legislation. Donald Trump was much more explicit about exploiting white identity than his predecessors in the Republican Party. White identity is at the core of his political base. Trump understands its importance and he knows how to take advantage of it. He is the most effective demagogue in our recent history.
Donald Trump does not seem to have any clear vision of governance. His presidency is all about maintaining his political base. He has attacked Republican leaders in Congress but not about policy issues. They have not provided him with the legislative victories that he needs to maintain his image as a powerful leader with a winning record. He also expects them to put an end to the Russian investigations. He seems to believe that he can secure his position within his base by holding campaign rallies and force Republican leaders to do whatever he wants. He is more powerful than Congress and they should do his bidding.