large constituency; populous electoral district; large group of voters
Used in political contexts to refer to an electoral district with many voters, or a large bloc of voters that can significantly influence an election.
This region is an important large constituency for the ruling party.
Whoever controls the large voter blocs controls the election.
Compound of 大 (large) + 票田 (voter base, electoral stronghold). 票田 itself combines 票 (vote, ballot) and 田 (rice field), metaphorically likening a constituency to a field that yields votes.