WASHINGTON (CNBC) – The harm caused by U.S. President Donald Trump’s first four years in office could be "even more profound” if he wins a second term, according to the president’s former national security advisor John Bolton. Bolton served in the Trump White House for 17 months between 2018 and 2019 and left on fractious terms. He authored a book on his time in the administration which characterized the president as ignorant of basic geopolitical facts and driven solely by desire for re-election, calling Trump "erratic” and "stunningly uninformed.” Bolton told CNBC on Wednesday that it became apparent during his time in the White House that Trump had no "philosophy” or "grand strategy.”