The Town Crier,
I did know that the second place winner used to be the vice-president. But in more recent times, presidential candidates have chosen running mates to broaden their appeal (as I stated above) and thus their electability. This has, as you & Joseph have noted, led to candidates choosing former rivals as running mates. But this wasn’t the case for President Obama’s choice of Ms. Clinton as Sec of State (one of the most powerful cabinet positions), since he’d already been elected at that point. Again, which presidents in recent times do you know of who’ve done this?