Former U.S. president Donald Trump pleaded not guilty on Tuesday to 37 federal criminal charges that he unlawfully kept national-security documents when he left office and lied to officials who sought to recover them. CBC’s Washington Correspondent Alex Panetta explains the evidence against him and the ramifications of this case for the next presidential election. For transcripts of this series, please visit: https://www.cbc.ca/radio/frontburner/transcripts