In the not so distant past, politicians would reach racist voters through what are sometimes called “dog whistle” comments. These are cautious, subtle statements that most people hear only as policy mumbo jumbo — criticizing affirmative action, say, or activist judges — but which others hear as reaffirmation of their bigoted worldviews.

How utterly different things are now, with the president of the United States deploying the oldest racist trope in the book by calling on four congresswomen of color to go back to where they came from. (Never mind that all four are U.S. citizens, and three were born in the USA.)

In so doing, Donald J. Trump is replacing the dog whistle with a bullhorn. He is all but declaring: I am a racist. I will advocate racist policies. I will redefine the Republican Party of Abraham Lincoln, Teddy Roosevelt and Ronald Reagan as the party of white grievance against a changing America.

To anyone who has been paying attention, Trump’s offensive comments, tweeted before a Sunday golf outing, were shocking but not surprising. Trump has trafficked in bigotry throughout his career in business and politics.