Senator Chuck Schumer, the majority leader, and Senator Joe Manchin III, Democrat of West Virginia, were both nursing resentments when they met secretly in a windowless room in the basement of the Capitol last Monday to try to salvage a climate package that was a key piece of their party’s agenda.

Mr. Schumer was discouraged that Mr. Manchin had said he wasn’t ready to do the deal this summer, and might never be. Mr. Manchin was frustrated that Democrats had spent days publicly vilifying him for single-handedly torpedoing their agenda.

“You still upset?” Mr. Manchin asked Mr. Schumer as their aides scoured the hallways outside to ensure the attempt at a truce would not be detected by other senators or reporters.