First of all, there's no mention of political parties in the Constitution, so you begin American history with not only no political conventions but also no parties.

Oftentimes during the period in which conventions really did business, you had situations where the delegates were divided and you would have ballot after ballot before there was a final nominee.

From the beginning of the presidential nominating conventions in the 1830's really through the 1950's, you had conventions that actually did real business.

Michael Beschloss Quotes