For much of his career, Biden built a reputation as a master negotiator. He’s known for his detailed knowledge of issues—and for hitting his stride when the pressure was on. Now, 81-year-old Biden is the oldest person to hold the presidency. WSJ's Annie Linskey and Siobhan Hughes go behind closed doors where some who have worked with him describe a president who appears slower.  Further Reading: - Behind Closed Doors, Biden Shows Signs of Slipping  Further Listening: - Inside the White House's Scramble to Avert a Bigger Middle East War  Learn more about your ad choices. Visit megaphone.fm/adchoices