THERE was only one person happier than Prime Minister John Major when he won reelection as head of Britain's Conservative Party Tuesday - and that was the leader of the opposition, Labour Party chief Tony Blair.
Mr. Major's victory, a beaming Mr. Blair said, meant that the ruling party would ''enter the next general election irrevocably split and under a wounded, unpopular, and discredited leader.''
Blair, and many analysts, say Major's majority was not large enough to end the virtual civil war in the party that pushed the prime minister to call a leadership election two weeks ago.
After a brief post-vote ''honeymoon,'' Major will soon come under fire again from within his party, especially on European policy, many analysts said.
Major will likely face difficulty over relinquishing the British pound in favor of a single European currency, and over his own problem of appearing a lackluster figure in domestic and international politics.
Yesterday, Major tried to exploit his win by moving swiftly to reshape his Cabinet. But even before he announced the changes, sources at Downing Street acknowledged that achieving a stable balance between the two wings of a divided party would pose problems.
Although 218 Conservative members of Parliament voted for the prime minister, 89 voted against and another 22 either abstained or spoiled their ballot papers.
This ''solid wedge'' of 111 members of Parliament, says political analyst Peter Riddell, shows that one-third of Conservatives in the House of Commons favored ''policies on Europe and taxation sharply different from those of the prime minister.''
John Redwood, the former Cabinet minister who opposed Major in the July 4 ballot, ''did much better than expected,'' Mr. Riddell says. His good showing would ''establish him in a leading position as the Right's spokesman.''
Mr. Redwood is hostile to the idea of a single European currency and is a strong supporter of downsizing government. According to columnist William Rees-Mogg, Redwood may have ''lost the leadership but won the intellectual crown'' of the Conservative Party.
White water ahead
Major also faces difficulty later this year when Jonathan Aitken, a leading member of the outgoing Cabinet, must address renewed charges that he was involved in unlawful arms sales to Iran and Iraq in the 1980s. Before yesterday's Cabinet reshuffle, Mr. Aitken said he was resigning his post.
Major's eagerness to refurbish his Cabinet reflects his wish to ''make a fresh start,'' one of his aides say. But the new mix of ministers seemed bound to underline the strength of his party's Euroskeptics in the wake of the leadership election. The prime minister appointed Malcom Rifkind to the key post of foreign secretary. Rifkind recently has been adopting a Euroskeptic posture, and his appointment is certain to be taken as a signal that Britain would fight against further unity.
The election seems likely to give Major only a brief respite from the party infighting that has made him the least popular British prime minister this century and placed the Conservatives 30 points behind Labour in opinion polls.
Major is claiming a ''clear-cut victory'' under his party's rules for leadership elections - a point Redwood accepts.
But privately, Conservatives are nervous about the very same calculations that are delighting the Labour Party and its youthful leader. Many Conservatives had hoped that by the next general election their party would be led by a more exciting political personality than Major - either Michael Heseltine, a Euro-enthusiast, or the charismatic Michael Portillo.
But now, Mr. Heseltine's friends say he has given up hope of ever leading the Conservatives. And Mr. Portillo, a prominent skeptic on Europe, was caught off guard by Redwood's entry into the leadership battle. Major has given him the post of defense secretary, apparently in the hope of keeping him as an ally.
''This leaves John Major looking terribly exposed,'' a senior Conservative member of Parliament said. ''He now has to prove that he can win the general election. On his track record over five years, frankly, I doubt if he can do it.''
Most leading British newspapers are equally skeptical and agreed that the real victor of the Conservative leadership contest is likely to be Blair. In other European capitals, there was little sign of pleasure at Major's victory. In Germany, the Stuttgarter Zeitung said Britain's Conservatives remained ''wedded to a vision of 'Little England.' ''