WASHINGTON — Republicans on Sunday inched away from President Trump amid mounting evidence that he may have sought to interfere in the federal investigation into Russian meddling in the 2016 election.

In a sign of growing anxiety, several important Republicans expressed discomfort with Mr. Trump’s firing of the F.B.I. director, James B. Comey, who had been leading the agency’s inquiry into whether Mr. Trump’s associates colluded with Russian officials. But the Republicans stopped short of explicitly criticizing Mr. Trump.

“If any president tries to impede an investigation — any president, no matter who it is — by interfering with the F.B.I., yes, that would be problematic,” Senator Marco Rubio of Florida, who is on the Senate Intelligence Committee, said on CNN’s “State of the Union.” “It would be not just problematic. It would be, obviously, a potential obstruction of justice that people have to make a decision on.”

Mr. Rubio and other Republicans hewed to a line repeated often on Capitol Hill last week: that they need more information about Mr. Comey’s termination, particularly in light of a report by The New York Times that Mr. Trump told Russian officials during an Oval Office meeting that Mr. Comey was a “nut job” and that his firing had “taken off” the pressure on the president.