You sure you're not thinking of Al Jolson (a good conservative Republican who wrote the Warren G. Harding campaign's theme song, btw!)?
No. Cantor did blackface also. I believe that it was fairly common in those days. Jolson is probably the one most identified as blackface.
Cantor's real name, Israel Iskowitz.. uh oh, there's an insult to the Palestinians too! The Obama crowd may go ballistic!