Freebird: Actually, that's the wrong citiation - it's referring to the Term beginning, which doesn't legally happen until he's sworn in on January 22 - that's when they legally become Prez and VP.
I ought to know, I did some research for my story "The Mine" about the scenario if both Prez and VP (along with most of the Federal Gov't) were killed in a nuclear cruise missile first-strike sneak attack on DC during the Inauguration and the East Coast right before they were sworn in.
What I found out was the Gov't would be in chaos, and if the "odd man out" were killed too, the COG would be hard-pressed to find a legal representative who could Constitionally be President. Once you're past the COG rules of sucession, it would take an act of Congress (which would require a quorum) to elect a President.
Odds are we'd find ourselves under Martial Law until things were straightened out if my scenario ever happened.
In the real world, If OB/Biden were both killed between Nov 11 (after the Electoral College vote was official - making them Prez and VP Elect) and Jan 22, Congress would have to vote on replacements from the Dem party. Once they're sworn in, COG takes effect.
Fleataxi