In the immediate aftermath of the shooting on Saturday, their conversation with the president led to a marked change in his language. Within hours, his remarks went from a vague statement — “if they had an armed guard inside, they might have been able to stop him immediately,” he said — to a plea to a rally crowd in Illinois to combat “the scourge of anti-Semitism.”

It was their advice to go to Pittsburgh on Tuesday despite the opposition of city officials and many members of the Jewish community. To lay the groundwork for the visit, they dispatched Jason D. Greenblatt, a White House aide who has worked with Mr. Kushner on a Middle East peace initiative, and Avi Berkowitz, who works for Mr. Kushner.

And it has been Mr. Kushner, in particular, who has been phoning Trump allies and encouraging them to support the president, who has grown frustrated over being accused of engendering a politically volatile climate.