WASHINGTON — A united front of top intelligence officials and senators from both parties on Thursday forcefully reaffirmed the conclusion that the Russian government used hacking and leaks to try to influence the presidential election, directly rebuffing President-elect Donald J. Trump’s repeated questioning of Russia’s role.

They suggested that the doubts Mr. Trump has expressed on Twitter about the agencies’ competence and impartiality were undermining their morale.

“There’s a difference between skepticism and disparagement,” James R. Clapper Jr., the director of national intelligence, said at a hearing of the Senate Armed Services Committee on the Russian hacks. He added that “our assessment now is even more resolute” that the Russians carried out the attack on the election.

The Senate hearing was the prelude to an extraordinary meeting scheduled for Friday, when Mr. Clapper and other intelligence chiefs will repeat for Mr. Trump the same detailed, highly classified briefing on the Russian attack that President Obama received on Thursday. In effect, they will be telling the president-elect that the spy agencies believe he won with an assist from President Vladimir V. Putin of Russia.