For a few weeks in late November, as speculation over whether President Donald Trump would fire his secretary of State, Rex Tillerson, reached a fever pitch, Trump and his chief of staff, John Kelly, also considered pushing out another top national security official: H.R. McMaster.

McMaster, the national security adviser who succeeded Michael Flynn — Trump’s first choice for the job, who resigned amid controversy within a month of taking office — has never quite clicked with the president, according to six senior White House officials. He is disciplined and focused, and has frequently clashed with Trump, who loves small talk and meanders from one subject to another…

Trump, according to two administration officials, was looking to tap former U.N. Ambassador John Bolton, whose frequent Oval Office visits ended when Kelly became chief of staff last summer. Kelly opposed his appointment, according to those officials.