Upset victory boosts political fortunes of Britain's third party

The third political force in Britain, the Liberal-Social Democratic Alliance, has succeeded in maintaining its recent upward momentum in British politics. Its latest triumph has come in a by-election for the Brecon and Radnor seat, which lies in the crumpled hills of mid-Wales.

The narrow win over the Labour Party, which had been expected to win at a gallop, underscores a persistent trend in recent months in which the Alliance invariably garners more votes than the polls anticipate.

Seldom have voters been so assiduously wooed as these in one of the largest and most beautiful constituencies in Britain.

Coming as it did after the government's major overhaul of social services, the vote was a critical test for the ruling Conservatives, who were defending this seat.

The government of Prime Minister Margaret Thatcher is in a trough at the moment, the sort of midterm doldrums that have affected most British governments.

The government's anxieties have been compounded by high unemployment and by public reaction to the changes in social services. Most people have taken the changes to mean they will get less from the government.

For the Labour Party, with the miners' strike behind it, the by-election was a chance to reassert itself as the major opposition party. Labour was confident it could win back a seat it had held before 1979.

The Alliance wanted to reaffirm its credibility as not just a refuge for disaffected Tory or Labour voters, but also a strong opposition party in its own right which could repeat its recent successes in county council elections.

Aside from Conservative, Labour, and Alliance parties, the voters had other choices. One candidate was Lord Sutch of the Official Raving Looney Party, who appeared to have jumped out of a Monty Python program.

The three main parties have rarely contested an election so keenly. With opinion polls predicting widely varying results -- one eve-of-election poll put Labour ahead by as much as 8,000 votes -- the result was awaited with more than the usual amount of suspense.

Although the Conservatives were widely regarded as fielding probably the most competent and most experienced candidate, they finished a poor third.

The Alliance win is especially troubling to Conservatives. They are worried that if their supporters become disillusioned, they are more likely to go to the Alliance than Labour.