On 28 April, by-elections were held to fill three vacant seats in Japan’s House of Representatives — and all were won by the main opposition Constitutional Democratic Party (CDP). These results have been reported as a crushing defeat for the long-dominant Liberal Democratic Party (LDP), which has been in power for all but five years since its founding in 1955 and won the past four lower house elections.

While the losses represent a setback for Prime Minister Fumio Kishida, few are predicting the LDP is at risk of losing office at the next general election.

The by-elections took place at an inopportune time for the conservative LDP. They were preceded by months of media coverage of dozens of the party’s legislators, including former cabinet ministers, having failed for years to fully declare donations at fundraising events. In response to opposition and media criticism, the party set up an internal disciplinary committee and censured 39 members of parliament on 4 April. But these measures are widely seen as inadequate, with even a significant proportion of LDP supporters expressing scepticism.

One of the by-elections was caused by the resignation of an LDP incumbent due to this donations scandal. Another took place after the LDP incumbent was arrested and charged for a separate campaign finance violation. Recognising it had little chance of winning in the face of a public backlash, the LDP did not put up a candidate in either district, effectively conceding two of the three seats even before the campaigns began.

The picture looks bleak for the LDP, with its support remaining below 30 per cent since the fundraising scandal broke in November 2023. Since then, monthly polls by Japan’s public broadcaster NHK have shown the Kishida government is supported by a mere quarter of the electorate, while more than twice as many survey respondents express disapproval. The extent of public discontent is evidenced in the Shimane district 1 by-election’s result, where the LDP nominee lost by nearly 20 per cent in a seat the party has held since its creation.

At first sight, the by-election results herald the possibility of an opposition victory in the next general election, which must be held by October 2025. Yet few are contemplating an incoming CDP government. Why is this?

While sweeping the by-elections boosted CDP morale, there is no evidence that it reflected a boost in CDP support. According to the NHK polls, the party has not scored above 10 per cent since 2018, and is only backed by 6.5 per cent of the electorate as of April. This is less than a quarter of the support for the scandal-plagued LDP.

While a smaller proportion of voters cast their ballots in by-elections than in general elections, the drastic decline in turnout in all three districts does not suggest a surge of enthusiasm for the CDP or other opposition parties. It is likely the CDP won on the back of discontent with the LDP rather than endorsement of its own platform.

The CDP is also far from the only vehicle for voters dissatisfied with the LDP. The anti-LDP vote remains fragmented, and prospects of the two largest opposition parties — the CDP and the libertarian Japan Innovation Party (Nippon Ishin no Kai) — joining forces is dim.

In fact, the Japan Innovation Party has openly declared its goal of replacing the centre-left CDP as the leading opposition force. Its poor performance in the recent by-elections has once again demonstrated its weakness outside the Kansai region, and dented its momentum, but is unlikely to alter this objective. Given the first-past-the-post, winner-take-all electoral rules for constituency seats in the House of Representations, a split anti-LDP vote only benefits the ruling party.

Further, the CDP has benefited from the Japanese Communist Party (JCP) not nominating its own by-election candidates. While the CDP can benefit from the votes of small but loyal and highly mobilised core Communist electorate, this cooperation not only presents a target for attacks from conservatives, but also divides opinions within the CDP itself. Warnings about a CDP–JCP coalition, which the CDP never proposed, likely contributed to its worse-than-predicted performance at the 2021 general election. In short, the CDP needs alliances with other opposition parties to win, but there are no obvious partners.

Dismal by-election results have ended speculation that Kishida might call a snap election in June. By the time the election eventually is held, the fundraising scandal may have faded from many voters’ memories.

The LDP may even replace Kishida, whose term as leader expires in September, with a fresher face such as former defence minister Shigeru Ishiba, former environment minister Shinjiro Koizumi or Foreign Minister Yoko Kamikawa — a tactic that has worked on previous occasions. The government’s key policies — such as a significant increase in defence spending — remain in place, and anyone hoping for a change of government has little reason to hold their breath.

Willy Jou is Associate Professor at the Faculty of Political Science and Economics, Waseda University. His research focuses on public opinion in Japan and other East Asian democracies.