In one sense it is the end of an era. Even if the coalition proves unable to agree on much beyond the need to oust the LDP, it is pledged to introduce reforms aimed at cleaning up Japanese politics. How much further it can go, or wants to go, is not yet clear. The prospective government quickly sought to reassure investors that it would not interfere with the LDP's record of economic achievement. Foreign allies are also being told that there will be no overnight change in Japan's policies, and the markets have been calm.
The seven-party 'non-LDP' coalition was yesterday joined by an eighth - the small trade union-based Rengo party, which has seats only in the upper house of the Diet. This simply emphasised the diversity of views in the grouping, which encompasses the Socialists, Japan's perennial opposition, and a number of more or less opportunist breakaways from the LDP, many of whom have few quarrels with their former colleagues on questions of policy.
Mr Hosokawa, although a senior member of the LDP for many years, is in a somewhat different category. He broke away to form his party 14 months ago, when it was by no means sure that Japan's post-war political dispensation was about to sunder. At the time he was thought to have condemned himself to irrelevance, but 12 days ago the Japan New Party won 36 seats in the lower house. After turning down a coalition offer from the LDP, he has used his base to gain concessions from the larger opposition parties.
The prospective prime minister is the descendant of feudal lords who held sway over the Kumamoto region of southern Japan. His maternal grandfather, Prince Fumimaro Konoe, twice served as prime minister in the 1930s and 1940s, committing suicide in 1945 on the day he was to have been arrested as a suspected war criminal by the Allied occupation authorities.
Mr Hosokawa served two terms as an LDP member in the upper house before becoming governor of Kumamoto prefecture, where he made a reputation as a clean and effective administrator. He would be Japan's second-youngest prime minister. A skiing champion whose good looks have given him a reputation as a womaniser, he makes a marked contrast to the aged incumbent, Kiichi Miyazawa. His relative youth and glamour would make it hard for the LDP to appoint another member of the corrupt old guard if it regains power, as it may well do.
Even if Mr Hosakawa's leadership proves brief, he will be credited with having begun a new era in Japan - as long as the coalition can enact legislation to stamp out corruption, ban political donations by companies and reform the electoral system to reduce politicians' need for huge campaign funds.
Ironically enough, Mr Hosukawa was regarded in his LDP days as a follower of Kakuei Tanaka, ousted as party kingpin in the 1970s in the first of many corruption scandals. Today the LDP is likely to choose as its new leader Yohei Kono, 56, who is regarded as a traitor by many party elders because he briefly defected in protest at Mr Tanaka's behaviour.
Leading article, page 19