Twenty-fifth Amendment to the United States Constitution
Tyler took the Presidential Oath, moved into the White House, and took over all of the old President's powers.  Nobody formally challenged Tyler's claim to the Presidency.  Eventually, both Houses of Congress passed a resolution saying that Tyler was the tenth President of the United States.  This created "the precedent of full succession."  A precedent is a rule or law that might be followed in the future if a similar situation came up again.  "Full succession" means that the Vice President would become the President, not Acting President, if the actual President died.  The "precedent of full succession" became known as the "Tyler Precedent."