I personally doubt that Trump will be able to pull off a right-left populist coalition. His views on women and minorities are unacceptable to nearly everybody on the left. There’s no evidence that he’s winning over many Sanders voters or downscale progressives.
But where Trump fails, somebody else will succeed. And that’s where he’s substantively revolutionary. The old size-of-government question was growing increasingly archaic and obsolete. In country after country the main battle lines of debate are evolving toward the open/closed framework.
If you don’t like our current political polarization, wait 10 years. One way or another it will go away. When the frame of debate shifts to open/closed, sometime soon, the old coalitions will smash apart and new ones will form. Politics will be unrecognizable.