Most Western commentators on Japan's recent change of leadership have focused on the extraordinarily short tenure of former prime minister Yukio Hatoyama, who resigned last week after spending fewer than nine months in office.

But for all of its brevity in office, Hatoyama's reign was by no means the shortest. Four prime ministers in post-war Japan have had even shorter tenures. And the previous three leaders from the former Liberal Democrat government each served only about one year (one should probably excuse Taro Aso, who naturally and properly resigned after losing an election).

It should be remembered that the Democratic Party of Japan (DPJ) and the Liberal Democrats both enjoyed huge majorities in the powerful lower house – in the LDP's case enough to muster two-thirds votes on key issues. They did not face votes of no confidence or losses on important bills, things that usually precipitate changes in leadership in other parliamentary democracies.

So why do Japanese leaders seem to have such a hard time holding on to power? I think that one can cite three major reasons.

The Key Role of Opinion Polls

The Japanese, as expressed in public opinion polls, are extraordinarily critical of their government. Public approval ratings for the cabinets routinely fall into the teens or even single digits. When Hatoyama resigned, his government's numbers had, in eight months, fallen from about 70 percent approval to 17 percent in one recent poll.

No American president has ever sunk so low. Even in the depths of the Watergate scandal, President Richard Nixon still commanded a public approval rating of 27 percent. Two other presidents thought to be supremely unpopular near the end of their terms, Jimmy Carter and George W. Bush, each rated about 35 percent approval.

The popularity of former Prime Minister Yoshino Mori (2000-2001) fell as low as 9 percent when he resigned after a gaffe-filled year in office. If there were a Guinness Books of Records category for the lowest approval ratings in any democracy, Mori would have won hands down. Eeven after his resignation, Mori nonetheless remained a powerful figure in LDP politics, reportedly influencing the decisions of a couple premiers to step down. He even managed to keep his Diet seat in the big wave election last year that saw the LDP ousted from power for the first time in a general election.

Panic sets in when public approval numbers fall that low. This is especially true if an election is looming, as there is now. Rank and file members start to get very nervous and worry whether they can survive the next election. A policy change of course seems too slow, and they begin to believe that only a change at the top and turn things around. Accordingly, polling for the new cabinet soared to 62 percent after Kan's election, an indication of the dislike voters felt for Hatoyama.

Soon the press picks up on this and begins a steady drumbeat of speculation as to how long the PM can hold out, and before along an air of inevitability builds up around the notion that the premier must take a fall for the good of the party.

Culture of Apology

In Japan it is expected that leaders, both in politics and business, resign to take the blame for missteps and perceived mismanagement even of their subordinates. The tableau of company officers bowing deeply in contrition is a staple of the newspapers and television news programs.

Sometimes they resign for what can only be considered pretty trivial matters. Naoto Kan himself resigned his position during a previous stint as party president because he had neglected to pay a couple months worth of national insurance premiums. He not only resigned his party post but he shaved off his hair, donned monk's garb and undertook a pilgrimage of penitence along a familiar Buddhist path of famous temples on the island of Shikoku (showing that among other things he has a certain flair for political theater.)

The flip side of the culture of apology is that a resignation does not necessarily mean, as it often does in America, political death or permanent exile from power. Politicians can and do make a comeback, or, like Mori, remain powerfully influential behind the scenes. Exhibit A is Prime Minister Kan.

Weak Sisters

Even so, one has to conclude that most of the recent Japanese prime ministers have been pretty weak sisters. Maybe it comes from being born with a silver spoon in their mouths politically speaking. Amazingly, the previous four premiers in a row were the sons or grandsons of past prime ministers.

Former Prime Minister Hatoyama was born with two silver spoons, coming not just from a famous and influential political family but also by being the son of an heiress to the Bridgestone Tire fortune. She funneled millions to her son's campaigns (which caused him some embarrassment as premier).

These premiers inherited their families' local political machines to ease their way into parliament and could count on a ready-made network of connections and help in climbing the greasy pole to the top. Whatever their good qualities they might have possessed, they lacked backbone.

Even the Japanese are disgusted with the way their leaders so easily shuck eir duties. Take the recent case of Yasuo Fukuda. He certainly faced frustrations on the job, such as the opposition controlled House of Councillors, the upper house of Japan's bicameral parliament. But then which world leader doesn't? President Barack Obama has frustrations too.

The new prime minister, often described as a "self-made" man, is cut from a different cloth. It's not that he was born in the Japanese equivalent of a log cabin – his father was a business executive. But he had no political connections to help him on his path. He ran unsuccessfully for the Diet three times before securing his seat. It shows that he possesses a kind of grit and determination that seemed lacking in his predecessors.

Being a parliamentary democracy, it is perhaps too easy for Japan easy to change leaders. Hatoyama quit on a Wednesday, and Kan was elected prime minister on a Friday. The trouble comes as the new leaders become more and more detached from the public as expressed in actually election results and not just poll numbers.

The LDP went through four prime ministers following its big electoral triumph in 2005 and its defeat in 2009. Only eight months in office, the new DPJ government has already had its first change of leadership. One change without an election might be excusable. Three or four begins to look like a bad habit.