Donald Trump is obviously not really a viable candidate for president. He is however hammering on issues that are frustrating the American public. Issues not being addressed by any of the other GOP candidates.
The public sees seemingly unchecked corruption and racketeering running rampant through the halls of power. People see corporate greed being rewarded as it eats the heart out of the nation. The public sees an evolving police state that seems to answer to no one. People see the pointless military adventurism that is the fuel feeding the hatred felt toward America around the world. American citizens feel discounted, not listened to, and pushed aside.
The Donald's stance on immigration is xenophobic; his thoughts on women's issues Neanderthal; and the very thought of him sitting down to talk to the likes of Putin or Merkel is very, very scary indeed. But, both the right and the left dismiss him at their peril.
Trump will go on gleefully gouging his finger into the eyes of all the Koch brothers' appointees until at least one of them gets real and starts talking about at least some of the real challenges facing this country.
Professional politicians laughingly dismiss Trump as a lightweight and blowhard, but he ain't goin' away any time soon. He's having too much fun.