opposition alliance; coalition of opposition parties
Refers to a formal or informal grouping of political parties not in government, working together to challenge the ruling party or coalition.
The opposition alliance is aiming for a change of government in the next election.
与党 refers to the ruling party or coalition in power, while 野党連合 is an alliance of opposition parties.
連立政権 is a coalition government formed by multiple parties, which may include both ruling and opposition parties; 野党連合 specifically denotes an alliance of parties not in power.
Compound of 野党 (opposition party) and 連合 (union, alliance).