Famously blunt, Kelly routinely commiserated with other staffers about the difficulties of working for Trump. “He can’t make up his mind,” the chief of staff once told aides. “He says one thing and does another thing. Look what I have to deal with.” Still, Kelly was considered a stabilizing force on Capitol Hill, where veteran lawmakers had been watching Trump’s presidency aghast. They saw Kelly, Mattis, and Secretary of State Rex Tillerson as essential guardrails for an erratic president.