In interviews with conservatives and Trump supporters across a half-dozen states, there were many theories about the president’s performance — he was tougher in private; he is cutting a mega-deal; he has a plan — and more than a few questions about his news conference with President Vladimir V. Putin of Russia, which left congressional Republicans and at least some voters struggling to endorse their leader’s approach.

“You’re essentially putting Russia first,” said Chris Ford, 26, a Republican in Dallas, tweaking a president who already had only his “lukewarm” support, as of this week. “It’s hard to see how that’s putting America first.”…

“We should stand our ground,” said Jimmy Treece, a retired construction worker and Trump supporter waiting for a bus in Carlisle, Pa. “There is clearly something wrong here.”

Russia, Mr. Treece said, was plainly “guilty of something.” But he hastened to add this: He hopes whichever candidates win in November will stand by the president, as he plans to.