“If you disagree with Bolton’s policy preferences, he is dangerous for three reasons: He is unafraid to start a policy fight in public, he knows how to pull bureaucratic levers when convenient, and he knows how to work around bureaucratic barriers when not,” said Loren DeJonge Schulman, a top aide to former Obama White House national security adviser Susan Rice.

Conservatives who share Bolton’s views say those qualities are an asset, arguing that he will empower a president who has long complained that his instincts on issues from the Iran nuclear deal to the war in Afghanistan get watered down by dissenting subordinates.

“He really knows how to make the system work,” said Elliott Abrams, who served as deputy national security adviser under George W. Bush. “One of the critical jobs of the national security adviser is making sure the bureaucracy implements the president’s decisions, and John knows exactly how to do that.”