Nick Confessore in the NYT:

The distance was magnified by the Supreme Court’s 2010 decision in theCitizens United case, which gave wealthy donors rising weight in Republican circles, even amid signs that the party’s downscale voters were demanding more of a voice.

Most of these voters had long since given up on an increasingly liberal and cosmopolitan Democratic Party. In Mr. Trump, they found a tribune: a blue-collar billionaire who stood in the lobby of a Manhattan skyscraper bearing his name and pledged to expand Social Security, refuse the money of big donors, sock it to Chinese central bankers and relieve Americans of unfair competition from foreign workers.