THE election of Yohei Kono as the new president of the Liberal Democratic Party (LDP) signifies it is placing its bets on a younger heavyweight to counter the populist appeal of prime minister-to-be, Morihiro Hosokawa. It also shows that the LDP Old Guard are losing their grip on the party, and factional considerations have diminished. Mr Kono, 56, defeated his only opponent - former foreign minister Michio Watanabe - by 208 to 159 votes in the party caucus. By the unwritten rules of LDP factionalism, Mr Kono's victory was a surprise as he does not lead a faction himself, and comes from the faction led by retiring LDP president Kiichi Miyazawa. Potential popularity seems to have been more important. Mr Kono was one of the ''Three Arrows'', the speakers from the second generation of LDP leaders who were most in the news in the general election. But the generation gap within the LDP over reform was probably more important. Mr Watanabe had long opposed reform and very likely his vote largely consisted of the Old Guard. Mr Kono, who as Chief Cabinet Secretary was the chief government spokesman during the second Miyazawa administration, has all along advocated political reform. His elevation to the party leadership may well have the effect of reducing LDP defections to the new coalition of former opposition parties due to take office next week. He now becomes the first LDP leader elected without the certainty of becoming prime minister. He comes from a famous political family - his father, Ichiro Kono, was a much-respected factional leader. Educated at the private Waseda University in Tokyo, and also at Stanford University in California, he was elected in 1967 for the first of eight successive times in a Kanagawa constituency south of Tokyo. The biting irony behind his elevation today is that had he stuck to his reformist guns, Mr Kono might well have been standing in Mr Hosokawa's shoes now, as the first non-LDP prime minister. In 1976, in the wake of the famous Lockheed Scandal involving former prime minister Kakuei Tanaka, Mr Kono left the LDP in protest and founded the New Liberal Club (NLC) to pursue reform. That year, the NLC won a striking 17 seats but was subsequently unable to improve on this. Mr Kono took the NLC into coalition with then prime minister Yasuhiro Nakasone when the LDP lost its majority in the 1983 election. He disbanded the NLC in 1986, rejoining the LDP. Had he stayed with the NLC, he could have been the crucial swing vote in the upper House of Councillors when the LDP lost its majority in 1989, and failed to regain it last year. More importantly, had he persevered with the NLC he would, as the first LDP defector, have been in a good position to ride the anti-LDP tide manifest in the recent election. Instead, Mr Kono now has to prevent that tide from further eroding the LDP's position.