Could Sherrod Brown or another non-primary candidate become the nominee in a brokered convention?

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19. Humphrey

had the largest number of delegates at the time of Kennedy's death, with 561 to RFK's 393 and Eugene McCarthy's 258. Only fourteen states held primaries in that year, the rest of the delegates were chosen at caucuses controlled by state party bosses.

We just don't have that kind of "smoke-filled rooms" politics anymore. For a non-primary tested candidate to be nominated, we would have to see many dozens of ballots with no clear winner. At that point, it would be an act of desperation.