The Liberal Democratic Party maintains a dominant position in Japanese politics while the opposition side is fragmented into many parties. Small opposition parties, namely the Communists, are still surviving even though it has been almost three decades since the 1994 electoral law reform, which made it difficult for such parties to exist. Fragmentation of the opposition is giving an electoral advantage to the ruling party. How can small opposition parties survive? An empirical analysis of voter survey data supports the argument that the controversy over a constitutional revision is playing a role in preventing anti-government voters from unifying under a single party.