The sudden illness of former Japanese Prime Minister Kakuei Tanaka, widely known as the ``shadow Shogun,'' is likely to hasten the passage of power to a new generation in the ruling Liberal Democratic Party. The present prime minister, Yasuhiro Nakasone, relies heavily on the Tanaka faction to stay in power. Six members of his Cabinet come from this faction, the largest by far in the ruling party.
Mr. Nakasone has 21 months to go before he must step down as president of his party and chief of the government. Of all Japan's postwar prime ministers, he has cut the most flamboyant figure on the international stage. He is a personal friend of Ronald Reagan and a warm admirer of Margaret Thatcher. He has sung songs with South Korean President Chun Doo Hwan and treated Chinese Communist Party chief Hu Yaobang to raw fish.
He is also popular at home, as polls have consistently shown.
But within the party, where deals are struck that determine the political longevity of a particular leader, Nakasone owes his position to the shadow Shogun. He could never have won office in 1982, nor been reelected in 1984, without Mr. Tanaka's forceful backing.
Tanaka's doctors have said that he should be back on his feet within weeks. But political analysts here say the illness only accentuates a process of generational change that had already begun within the Tanaka faction and within the party as a whole.
Last month, Finance Minister Noboru Takeshita challenged the former prime minister by starting his own ``study group'' within Tanaka's faction. Mr. Takeshita is regarded as Tanaka's most able lieutenant and most likely successor. Modest in public demeanor, Takeshita has been effective as finance minister. He is said to have felt frustrated over his mentor's unwillingness to hand on his baton, even though Tanaka himself, having been convicted of bribe-taking in the Lockheed scandal of the mid-1970s, is unlikely ever to hold public office again.
With 121 members -- nearly a third of the Liberal Democrats' total strength in the parliament -- the Tanaka faction has both the numbers and cohesion to make or break cabinets. So far, all decisions on such matters have been made by Tanaka himself.
Takeshita's challenge means the emergence of an alternative decisionmaking pole within the hitherto monolithic faction. The shadow Shogun's illness is expected to hasten this process, and thus to speed the day when the Tanaka faction will no longer be content to be kingmaker without providing the king.
Not long ago, Takeshita was asked to present a piece of calligraphy to the national press club of Japan when he gave a speech there. The phrase he chose was waga michi o yuku, which may roughly be translated as ``going my way.'' Although he explained that he intended to move forward in modesty and forbearance rather than in arrogance or pride, many journalists present took the phrase as a portent of his future within his faction and the party.
Two other factions -- those headed by former Prime Ministers Zenko Suzuki and Takeo Fukuda -- have already anointed crown princes as potential candidates when Nakasone's term expires in the fall of 1986. The Suzuki faction's candidate is former Foreign Minister Kiichi Miyazawa. The Fukuda faction's candidate is Foreign Minister Shintaro Abe.