Whether you have studied Japanese politics for years or you are only a casual observer, you are bound to have heard of the "danger zone" for Japanese prime ministers. As media reports and analysts have suggested, this is the zone in which a prime minister is at risk of leaving office, and it begins when public approval falls below 30 percent. But is there really a danger zone, and if so, what does that really mean?

Public opinion can be a problematic measure, so it is one that many scholars and practitioners often dismiss. Even in Japan, polling is imprecise and varies across different media outlets. Generally, they each target only about 1,000 to 2,000 respondents in every poll — 0.001 percent of the population — and the mode of communication (e.g. landline versus cell phone) for contacting respondents can affect the polling sample. In short, one can hardly claim polls as conclusive facts about public sentiment.

However, one thing about Japanese polling is that it is consistent. The media outlets that conduct these polls do so every month, with special polls in the event of elections, controversial legislation entering the Diet, or other significant events. This consistency is important because it provides a constant indicator to politicians. The fact that these numbers matter to them is why public opinion is able to influence Japan’s political institutions.

How do polling numbers influence Japanese politics? The answer to that question comes from looking at how Japanese political institutions operate. As many will know, one single party — the Liberal Democratic Party — has predominated the Diet over much of the period since 1955. That single party is not monolithic though; it is composed of many factions, each with different leaders who would like their own shot at becoming prime minister (or choosing one).

The party picks its president to become the prime minister, which is why they say to become prime minister in Japan, a candidate must win a "majority of a majority": the party must win the majority of seats in the Diet and the candidate must win a majority of votes from within the party.

This system is what actually puts the prime minister at risk when public approval tanks. First and foremost, there is always jockeying within the LDP anyway, so polling numbers become tools for intraparty rivals to achieve their individual objectives.

Second, even though every politician brings different ideas and priorities to the table, they all can agree on one thing: the importance of keeping their jobs. When a prime minister’s approval is dropping, it tends to pull down the public approval of the party at the same time, inviting support for opposition parties.

If the party cannot right the ship, it eventually allows for opposition parties to steal seats in elections or wrest control of the government away (which they did in 1993 and 2009). Thus, when public opinion drops, allies within the party start to reconsider their priorities and rivals begin ramping up their scheming. If the prime minister cannot reverse the trends, the party takes steps to replace its president, causing a change in administration.

So if public opinion matters, does the “danger zone” start when approval ratings dip below 30 percent? Historical data merits this description. For example, NHK’s historical polling data shows that of the last eight prime ministers, only two — Junichiro Koizumi and Shinzo Abe — bowed out with public approval higher than 30 percent. Meanwhile, the approval ratings of the others at the time that the rest left office were well below that: Yoshihiko Noda (20 percent), Naoto Kan (18 percent), Yukio Hatoyama (21 percent), Taro Aso (15 percent), Yasuo Fukuda (20 percent), and Yoshiro Mori (7 percent).

In examining public opinion, the breakdown I usually recommend is as follows. Anything higher than 50 percent is the “command zone” — the prime minister will have stable control of the LDP and the administration’s policy agenda. Between 40 and 50 percent is the “comfort zone,” meaning the prime minister has some political maneuver space but must give heavy consideration to the interests of allies and rivals within the party. Beneath that, the 30 to 40 percent range is the “caution area”; 20 to 30 percent is the “danger zone”; and less than 20 percent is the “how are they still in office?" zone.

When a prime minister reaches the caution zone, the quickest fix is a Cabinet reshuffle. As long as sufficient time has passed since the previous reshuffle — at least a year — the public tends not to look at it as political gamesmanship, even if sometimes that is all it really is. A Cabinet reshuffle done well can yield as much as a 10 point boost in public approval ratings, meaning it could easily bump an administration up one level; e.g. from caution to comfort.

The second option is a snap election. Abe has used two snap elections to his advantage in December 2014 and October 2017. By dissolving the Lower House, the prime minister can force a general election. One would think that doing so amid falling support numbers is a bad idea, but the speed of the election is key. Because a snap election happens within a month of the Diet dissolving, opposition parties who are unprepared find it difficult to scrounge together candidates, raise the necessary monetary deposits for those candidates, prep campaign materials and develop a policy platform — all herculean tasks even without the compressed schedule.

Given this, whenever there is any speculation about whether the prime minister is going to call for a snap election, you will see reports in the media about opposition parties preparing for it, even if the actual likelihood of it happening is low. When snap elections result in the ruling coalition maintaining or gaining seats, it usually provides a corresponding bump in the polls.

This is why you will be seeing speculation in the media as to whether Abe will call for a snap election in the coming months. The fact that his public opinion remains in the 30 to 40 percent range (the caution area) means that party leaders will be looking at potential courses of action to reverse the trend. This in turn means that Abe will consider a Cabinet reshuffle or a snap election.

Because the LDP will want to keep opposition on its toes, few will know for sure which option the Abe administration will take. Whatever the case, Abe has been in this position several times before and has defied expectations, so do not assume that he is in the danger zone just quite yet.

Michael MacArthur Bosack is the special adviser for government relations at the Yokosuka Council on Asia-Pacific Studies. He was deputy chief of government relations at Headquarters, U.S. Forces Japan.

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