London — For the Reagan White House, a gleam of good news from Western Europe: While Washington worries about the state of the NATO alliance, a European lack of confidence in President Reagan, cruise missiles, and the outcome of the West German elections, its best friend on this side of the Atlantic is still riding high.
In the wake of new trouble inside the opposition Labour Party, the political outlook for British Prime Minister Margaret Thatcher is better now than had been expected.
That means, from the Reagan viewpoint, that Britain is likely to remain a base for cruise missiles for another five years at least, a strong supporter of American policies toward the Soviet Union, a firm base from which American capital can flow into Western Europe, and welcome cement in the European alliance with Washington.
Each one of these roles would be called into question if Mrs. Thatcher should lose the next general election (which must be held before May next year and will probably be held this year).
The Labour Party is committed to policies opposing cruise missile deployment here, canceling Tory plans to buy Trident submarine missile warheads from the United States, and removing all American bases from Britain.
If the Liberal-Social Democratic Alliance should hold the balance of power, with Labour having the most number of seats, then cruise missiles would be more likely to be deployed and American bases would stay, though Trident would still be opposed. The situation would depend on the actual numbers of seats involved.
At the moment, however, Mrs. Thatcher's hopes of winning the next election still look very good.
Each day that goes by produces a new crop of headlines and television reports showing the Labour Party locked in battle between its right wing, its traditional left wing, and its new far-left members, mostly young activists at the grass-roots level.
Labour's leader, Michael Foot, is in a weak position, assailed from both right and left within his party, and having to declare time and time again that he will not step down in favor of his deputy, Denis Healey.
Until Feb. 24, opinion polls here showed Mrs. Thatcher leading Labour by margins ranging from 21 percent (a Marplan Poll for the Guardian newspaper said it was 49 to 28 percent in a Feb. 7-9 poll) to 13 percent (a Market Opinion and Research International called it 45 to 32 percent), and 11 percent (a mid-February Gallup Poll for the Daily Telegraph called it a 43.5 to 32.5 percent lead).
Then came the shattering defeat for Labour in the Bermondsey by-election Feb. 24 - a working-class dockland area in London that Labour had held for 60 years. The seat was taken by a Liberal candidate running for the Liberal-SDP Alliance.
The next day, the London Sunday Times commissioned a new Market Opinion and Research International (MORI) national poll, published Feb. 24. Labour, at 26 percent, had dropped six points from the previous MORI Poll, and the Liberal-SDP Alliance leapfrogged into second place by gaining 13 to 34. The Conservatives also fell by six points, to 39 percent.
These figures need to be taken with caution, however. Bermondsey was a special case, political analysts here say, fielding 16 candidates and a Labour man nationally controversial because of his far-left views.
Mrs. Thatcher is still out ahead. Labour is deep in trouble, and the question is whether the Liberal-SDP Alliance can keep its momentum. Never before had it taken a seat away from Labour.
Attention has now turned to Darlington, in Durham, where Labour has called a by-election March 24 to try to restore its sagging fortunes. Labour held the seat by a razor-thin 1,000 votes at the last general elections in 1979. Ominously, a local poll published in the Mail on Sunday Feb. 24 showed Labour trailing far behind with 25 percent of support. The alliance had 38 percent and the Tories 37 percent.
An alliance win would be a more significant boost than the one in Bermondsey.
Labour still carries residual electoral support in northern England, in Scotland, in Wales, and in Northern Ireland. Just before the Bermondsey vote, it held onto its seat in neighboring Peckham, in London.
But Bermondsey was a huge defeat, nonetheless, and the right-wing press here is trumpeting Labour's troubles.
Instead of rallying the country in a crusade against a government whose term of office has seen unemployment shoot to record levels, Mr. Foot is having to fight to retain his job. White-haired, bespectacled, donnish, and a passionate supporter of British nuclear disarmament, he is a man beset. His ineffectiveness on television is one of Mrs. Thatcher's main political advantages.
After several years he is still deep in a fight with his far left wing. The constant infighting has caused a drop in the opinion polls, and led directly to four of the party's biggest names - Roy Jenkins, Shirley Williams, David Owen, and William Rogers - forming the breakaway Social Democratic Party.
The MORI poll Feb. 24 showed 58 percent of those questioned saying Mr. Foot should resign, and 32 percent that he should stay; 69 percent were dissatisfied with the way he was doing his job.