Kaifu administration. The three together became known as "YKK" after the initials of their last names. Originally the trio had agreed to sway their factions towards the new generation of LDP leaders, and marginalize the old guard within the Diet. With the election of Miyazawa (then leader of Kato's own faction) in 1991, YKK gained greater prestige and power within the party. From the Miyazawa era onwards, YKK represented the power base of the anti-mainstream faction in the LDP. All three leaders made repeated tilts at the party leadership in the 1990s, but were unsuccessful. In 1998, Kato assumed leadership of the Kochikai faction, taking over from Miyazawa. In May 2000, upon the sudden illness and death of Prime Minister Keizō Obuchi, Kato did not make a challenge for leadership of the LDP, believing that internal strife would not be healthy for a party in mourning. By November, however, displeased with the slow pace of reform and poor public image of the Mori administration, Kato made his move. After consulting with the opposition parties, Kato realized that with support of his and Yamasaki's factions, a vote of no-confidence against Mori would pass in the Diet. Initial public reaction to Kato's announcement of this vote was good, with Mori's approval ratings diving to 30%. Unfortunately for Kato, the LDP Secretary-General at this time, Hiromu Nonaka, was a strong supporter of Mori. Nonaka launched a harsh round of party discipline, threatening to expel any LDP members that voted against Mori, and his threats had the desired effect: Kato's support dried up even within his own faction. Kato and his remaining supporters abstained from the no-confidence vote as a face-saving measure, knowing that he could not win. However, the damage had been done with Kato and Yamasaki left to bear the full brunt of public humiliation. The aftermath of Kato's rebellion was disastrous as a large segment of his faction split off, weakening his influence in the Diet. Public opinion that had initially supported ousting Mori now blamed Kato for his failure. The opposition parties were frustrated with his unwillingness to break from the LDP. Both Kato and Yamasaki had been considered candidates for Prime Minister, but with the loss of prestige resulting from the Mori affair, they had lost their chance. With Nonaka's resignation shortly after Kato's rebellion, the path was clear for someone to replace Mori. Junichiro Koizumi, the only member