While reading The Death of a President, a second-by-second account of the assassination of JFK, I came across an interesting Constitutional issue.

When exactly does the Vice President become the president when the Chief Executive dies?

LBJ thought that he wasn’t legally president until he took the oath of office. In other words, for more than an hour after JFK’s death, the United States did not have a Chief Executive. (JFK was pronounced dead at 1 pm CST, Johnson took the oath at 2:38.)

It’s a popular misconception, but according to the Constitution’s text, Johnson became president the moment JFK died. The taking of the oath is ceremonial.

Just as Joe Biden became president at noon on January 20, regardless of the moment the Chief Justice administered the oath.

But there’s another Constitutional issue, one that has not been fully resolved, but one which practice over the years has gelled into acceptance. And that’s whether the VP becomes the president… or only the acting president serving until a new election is called.

When John Tyler became president after the death of William Henry Harrison, he believed he had fully assumed the presidency. Some Senators argued he was only acting president, and he had to call a new election.

The wording of the Constitution was so vague on that point that neither side could prove their case. Tyler’s view eventually won out, both houses Congress eventually adopted a resolution confirming it, and it has become precedent.