As Democratic senators gathered on Tuesday for their closed-door weekly luncheon, they heard from their California colleagues, Alex Padilla and Adam Schiff, who carefully differentiated between isolated cases of vandalism in Los Angeles and the larger number of peaceful protesters who swarmed the streets to oppose President Trump’s deportation efforts.

At roughly the same time, Mr. Trump was across town in the Oval Office unspooling stories of violence, asking the assembled cameras, “Did you see the guy throwing the rocks at the police cars?”