Polls by leading dailies in advance today’s vote all point in the same direction, predicting that the DPJ can win at least 300 seats, coming close to a supermajority of its own, while the LDP is in danger of falling below 100 seats–with a number of senior LDP politicians, who have rarely had to sweat reelection, fighting for their political lives against young and (often female) DPJ challengers.

But what explains the enormous pendulum swing in Japanese politics? The answer isn’t as puzzling as it might seem.

In 2005, the Japanese public was not voting for the LDP and it was not voting for postal privatization, the issue that was the basis for Koizumi’s calling the election. It was voting for Junichiro Koizumi, not just Koizumi the man–although Koizumi’s quirky charisma and hair were certainly part of his appeal–but for the type of politics that Koizumi represented.

In 2001 the LDP was deeply divided, led by the widely detested Yoshiro Mori. Since returning to power in 1994 (it was out for only a little more than a year), the party had overseen a worsening economic crisis even as the government went deep into debt trying to revive the economy through pump priming. The ramifications of Japan’s aging, shrinking population were coming into view. There was a widespread sense of worsening quality of life and growing inequality in the relationship between Tokyo and the provinces, in income, and in economic opportunity. The LDP appeared incapable of fixing any of these problems, and the creation of the DPJ in 1998 suggested that an alternative might be in the offing.

Then Koizumi rode into power in 2001, on the wave of support from the party’s local chapters. He signaled a break from the LDP’s traditional machine politics and sought to strengthen the power of the prime minister at the expense of the party and its factions. He wanted to appeal directly to the public in his campaign against what he called the LDP’s ‘opposition forces.’ In short, he signified change.

The public rallied behind the prime minister because he signaled a brand of governance in which the prime minister and the cabinet would be able to establish policy priorities and follow through on them, without bending to the will of party barons, bureaucrats, or interest groups. It was for this reason that Koizumi’s expulsion of LDP members who voted against postal privatization in August 2005 was significant: Koizumi was signaling that it was the prime minister who decided policy, not party notables.

Not surprisingly, in a poll taken after the election in 2005 by the Asahi Shimbun, 58 per cent of respondents viewed Koizumi as the reason for the LDP’s victory, compared with only 18 per cent who cited support for the LDP.

A year later, however, Koizumi had left the premiership, handing over the party to his chosen successor, Shinzo Abe, who promptly agreed to readmit the so-called ‘postal rebels’ who had been banished by Koizumi. The old LDP was back. In the three years since Koizumi left office, the LDP rule has once again been characterized by widely unpopular cabinets hamstrung by the party and controlled by the bureaucracy. Also, many of the problems present when Koizumi took over in 2001 remained, and had indeed worsened in the interim despite a long period of (export-led) economic growth.

The 2009 general election, then, has been driven by the same desire for effective government that led the public to rally behind Koizumi in 2005–this, despite polls showing substantial skepticism regarding the DPJ’s policy program and its ability to change Japan for the better. The LDP has shown itself to be incapable, and the DPJ, for all the doubts about its manifesto, is promising a new form of government in which addressing the economic insecurity of the Japanese people is the top priority.

But while the Japanese people appear ready for ‘regime change,’ the DPJ’s slogan, they don’t seem to want radical change–but rather change in the sense elaborated by former DPJ leader Ichiro Ozawa: ‘change so that things remain the same.’ Or, in this case, so that things might be as they once were.

This article was adapted from a version that appeared here at The New Republic.