A lot has been written about the close relationship between Barack Obama and Joe Biden.

Obama has repeatedly said that choosing Biden was the smartest decision he has made in politics. And, at the funeral for Beau Biden, the vice president's oldest son, the president said of his running mate: "Joe, you are my brother.  And I’m grateful every day that you’ve got such a big heart, and a big soul, and those broad shoulders.  I couldn’t admire you more."

Given that relationship, it was compelling to watch Biden, age 72, end a lifelong dream with Obama, a man 18 years his junior and one who had achieved that dream, standing by his side. "I believe we're out of time, the time necessary to mount a winning campaign for the nomination," Biden said as Obama stood silent a few feet away. "But while I will not be a candidate, I will not be silent."

Biden's speech felt like the address he wanted to give to launch a campaign for president, but knew he couldn't.  The timing wasn't right -- and  won't be. Obama, of course, knew all that -- and knew that, for him, the timing had been perfect.

How do you comfort an old friend who has to let a dream drift away? You put a hand on his shoulder.