Some conservative activists who had pushed for the Senate to ban the filibuster entirely said they had been betrayed by Republican moderates.
"Once again, moderate Republicans have taken the victory and thrown it overboard," said Paul Weyrich, a veteran conservative organizer, who predicted that conservatives voters would punish the party.
Mr. McCain said he expected that interest groups on both the left and right would be furious at the compromise.
"Think of all the money they are going to lose," he said, ducking into a car to head to the premiere of a film about his life, referring to the fund-raising operations that had sprung up around the judicial battle.
After thanking Mr. McCain on the Capitol steps for the "wonderful" deal, Senator Barbara Boxer, Democrat of California, acknowledged that Democrats had cleared the way for possible confirmation of three judges many in the party opposed. But Ms. Boxer said others had been held off, and she described the agreement as a "big victory" for Democrats.
Democratic officials said an unwritten aspect of the pact is that two nominees not named in the deal - Brett Kavanaugh and William J. Haynes - would not be confirmed and would be turned aside either at the committee level or on the floor.