In interviews across the country over the last few days, dozens of Trump voters, as well as pollsters and strategists, described something like a bonding experience with the president that happens each time Republicans have to answer a now-familiar question: “How can you possibly still support this man?” Their resilience suggests a level of unity among Republicans that could help mitigate Mr. Trump’s low overall approval ratings and aid his party’s chances of keeping control of the House of Representatives in November.

“He’s not a perfect guy; he does some stupid stuff,” said Tony Schrantz, 50, of Lino Lakes, Minn., the owner of a water systems leak detection business. “But when they’re hounding him all the time it just gets old. Give the guy a little.”

Republican voters repeatedly described an instinctive, protective response to the president, and their support has grown in recent months: Mr. Trump’s approval rating among Republicans is now about 90 percent. And while polling has yet to capture the effect of the last week’s immigration controversy, the only modern Republican president more popular with his party than Mr. Trump at this point in his first term, according to Gallup, was George W. Bush after the country united in the wake of the Sept. 11 attacks.