two-partyism

uncountable

(politics) A political system in which voters are given the choice between two parties.

Japanese Meaning

二大政党制 (有権者が二大政党のいずれかを選択する政治体制) / 二大政党政治体制 (同上)

Many voters criticize two-partyism for limiting political choices and marginalizing smaller parties.

多くの有権者は、政治的選択肢を制限し小規模政党を周縁化するとして二大政党制を批判している。

Sense（1）

(politics) A political system in which voters are given the choice between two parties.