Sen. Kamala Harris of California, who officially kicked off her campaign Monday on the symbolically resonant Martin Luther King Jr. Day, has criticized Trump’s rhetoric, divisive positions and style as commander in chief. But she often does not mention his name; she speaks about restoring the “nobility of the office;” and she has so far avoided provoking him on Twitter at this early stage.

Sen. Cory Booker of New Jersey is ignoring the President. Independent Sen. Bernie Sanders of Vermont took the most aggressive approach on Monday, calling him a “racist.”

After concentrating on introducing herself to voters in her first swing through Iowa, Sen. Kirsten Gillibrand of New York stepped up her attacks on Trump, accusing the President of adding fuel to a “very ugly fire” of racial, religious and community divisions.

And former Housing and Urban Development Secretary Julian Castro is presenting himself as the “antidote” to Trump.