Felix Ehrenhaft made a claim that he saw electric charges smaller than an electron. In that respect he was ahead of his time. Far ahead, as quarks haven't been detected yet directly.
His measurements were controversial though and Millikan was passed over for a Nobel prize because of this. Even Ehrenhaft's friendship with Einstein ended because of this! That's why I call it bitter.
Ehrenhaft was quite a character and he claimed to have discovered magnetic monopoles and magnetic currents. He was right about fractional charges. Later on quarks were (indirectly though) observed.
When and why the controversy ended? It ended in favor of the view that the electron is the only basic charge to be discovered directly, I guess. But nevertheless, quarks exist. Were they known when the controversy ended?