The onus to chart a path would fall first on the candidates themselves, who could opt to break with tradition and name their choices without the nomination locked up. This would not be unprecedented, and not without risk, however: They could lose leverage to strike a deal at the convention, appear presumptuous, or alienate delegates with their pick.

Conversely, the number-two slot could be used as a bargaining chip to strike a deal to win the nomination. If a nominee emerges without first forging some sort of unity ticket, however, the selection responsibility would fall to the party, either through a vote on the floor or by giving the nominee time to make his own last-minute pick.

“If a candidate were very close on the first ballot, but doesn’t have 1,237 delegates, the greatest single tool they have on the second ballot is to bestow the vice presidency on someone,” said one Republican strategist.

There is even a chance that the nominee could delay picking his running mate until after the convention to allow for the lengthy vetting process that has become standard for vice presidential picks.