Prosecutors in Donald Trump's criminal trial call their first witness: a former National Enquirer publisher who puts the former president at the center of a conspiracy to corrupt the 2016 election. Joe Biden wins a major endorsement from the building trades unions and works to define Trump as an out-of-touch rich guy who only wants to help his rich friends. In Pennsylvania, Connecticut hedge fund manager Dave McCormick officially wins the Republican nomination for Senate and will face Democratic Senator Bob Casey in the fall. Then, George Stephanopoulos talks with Dan about the challenges of covering Trump, his new book about the White House Situation Room.