bloc / block
A political or voting group versus the ordinary word for a mass, a street, or an obstruction.
A bloc is a group united for a purpose: a voting bloc, the Eastern bloc. Block is the general word: a cube, a city block, a block of wood, block the door. Write bloc voting only when you mean voting as a unit. Write block voting only when you mean something else—blocking a vote, or votes by city block.
Examples
UseThe farm bloc held the bill.
UseThey live on my block.
AvoidThe farm block held the bill. (If you mean the coalition.)