Moderator Martha Raddatz, left, reaches across to greet Republican vice presidential candidate, Rep. Paul Ryan, R-Wis., right, as Vice President Joe Biden, center, takes his seat for the start of the vice presidential debate. (AP Photo/Pablo Martinez Monsivais)

Photo by: Pablo Martinez Monsivais

Moderator Martha Raddatz, left, reaches across to greet Republican vice presidential candidate, Rep. Paul Ryan, R-Wis., right, as Vice President Joe Biden, center, takes his seat for the start of the vice presidential debate. (AP Photo/Pablo Martinez Monsivais)