As the Conclave grows closer, the mutability, during the last century or so, of the rules governing conclaves acquires more and more interest.
Since Pius XII, it has become almost the custom for each incoming pope to alter the rules bequeathed to him by his predecessor. The reason why this has rarely appeared to matter very much has been that those rules that have most tempted so many pontiffs to make changes [see Wikipaedia], mostly concern the means to be taken to secure a result at the end of a contentious conclave in which normal procedures have failed to deliver, er, the Bacon of a necessary two-thirds majority.
And the desire of Cardinal Electors to enable a decorous succession has apparently led them to decide fairly soon into a conclave that, since X is pretty clearly going to get his majority eventually, it looks better if it's given to him sooner rather than after a long agony.
But there was a problem when Benedict XVI followed S John Paul II. The way matters stood then was that, if a two-thirds majority were not secured after the normal rules had been followed right to their very end, a new procedure then took over which could result in the next pope being elected on a simple majority.
You see, suppose candidate X had got an overall majority, but which was a majority which fell short of being two-thirds.
What comes next?
All that the majority cardinals supporting X then needed to do was to sit back and pick their noses and just wait until this conclave reached the stage when the move had formally to be made to a simple majority. Then their man would slide comfortably in to the sedes stercoraria.
This breached the established principle that a pope needed a two-thirds majority ... a principle ancient enough to have acquired auctoritas. Moreover, a pope incapable of securing office except as the result of this extreme procedure would hardly be embarking upon his pontificate with his own auctoritas entirely intact. People would say "He only got in by ... ... ".
So Benedict XVI restored the principle that a two-thirds majority would, after all, always be necessary.
That is where we are now.