ð Share this article The nation on course to choose female prime minister in landmark first Over the last two decades, Japan has had more than 10 leaders. In fact, a specialist compares assuming the country's highest office to drinking from a "poisoned chalice". But why does the country keep changing prime ministers? It's due in part of it being a "one-party democracy", explains Professor James Brown of Temple University in Japan. The LDP's grip on the country's politics means the main political competition originates within the party, rather than from external parties. "So within the LDP there are intense conflicts within various groups - they all desire their own faction to secure the top job." "So even though you might be chosen as prime minister, the moment you're in power, you have many individuals scheming to try to get you out again." Key Factors Behind Frequent Changes Single-party rule limits outside challenges Party infighting drive leadership contests The prime minister's position is often described as a "poisoned chalice" Political stability stays elusive despite financial power