Still reeling from loss, Biden wrestles with 2016 decision

In painfully public fashion, Biden is wrestling with whether to close the curtain on a political career that's spanned nearly half a century, or to fight one last fight for the job he's always wanted.

Confounding Biden's decision about 2016 are emotional aftershocks from his son's recent death, which Biden has begun to discuss publicly in a stunning instance of a politician unmasking his own frailty.

Whether Biden, over the next weeks and months, can muster the emotional strength needed to campaign for president at full speed remains the biggest question in his deliberations, several of his advisers say.

Part and parcel to that consideration is the toll a campaign could take on his family, say the advisers, who requested anonymity because they weren't authorized to discuss the topic publicly.

On the anniversary of the Sept. 11 terrorist attacks on Friday, he expressed deep gratitude to firefighters in Manhattan who offered him consolation over his son's death.

Having established a litmus test for presidential candidates - they must be "willing to give it 110 percent of who they are" - he would have to explain what's changed after saying this week that he'd "be lying if I said that I knew I was there."