In the spring of 1979, when Margaret Thatcher and the Conservative Party tackled the Labor government headed by Jimmy Carter's friend James Callaghan, there were some interested Americans watching. Republican National Chairman Bill Brock and several aides flew over to see how the Tories went at it.

After Thatcher's victory, Brock invited the architects of the Tory campaign to show an 80-minute film summary of their work and discuss its implications with Republican congressmen and politicians. Borrowing shamelessly from their themes and techniques, Brock in early 1980 launched a $5 million ad campaign, ridiculing the record of the Democrats and urging people to "Vote Republican -- for a Change." The Republican victory in 1980 was based largely on Thatcher's themes, which broke into the normally Democratic blue-collar vote.

Now it is the spring of 1983, and Ronald Reagan's friend Thatcher is putting her 4-year-old government to test at the polls next Thursday, under economic conditions far worse than anything the Republicans contemplate facing when their turn arrives in 1984. While inflation in both countries has been cut to around 4 percent, unemployment in Britain has doubled under Thatcher to an official 12.8 percent -- drawfing the rise from 7.4 to 10.2 percent under Reagan.

Yet all the polls this weekend predict that the Tories will not only stay in power but probably increase their majority in parliament. So the Republicans' researchers are here watching again.

But not just Republicans. Peter D. Hart, the pollster for Democratic presidential hopeful Walter F. Mondale and strategy adviser to the congressional Democrats, just ended a visit here shaking his head at the way in which Thatcher is powering her way to a second term. "The message and dynamics of this campaign have a lot of lessons for the Democrats," Hart said this week, "and none of it is particularly good news."

The temptation to find parallels from Thatcher to Reagan is overwhelming, for it is no accident that they have been drawn to each other. Both are self-described "conviction politicians," with a deep distrust of the Soviet Union, a deep belief in private enterprise, and a deep aversion to big government and high taxes. Both have suffered through mid-term economic and political slumps -- hers much worse than his. Both have perservered on their main lines of policy, despite the public skepticism and resistance of more conventional fellow-conservatives.

But there are also obvious and important differences between the two countries, the two parties and the two leaders, which limit the analogy. British voters are not Americans. Though political scientists here find evidence that class and party loyalties are eroding, they remain stronger than in our country.

Their electoral system is different. Control of Parliament and thus the government is decided by winner--take-all local contests in more than 600 constituencies, only a fraction of them closely fought. It is a three-way race this time, with Conservatives and Labor joined by the Alliance of Liberals (who usually win only a handful of seats) and Social Democrats who broke away from Labor when it swung far to the left after its last defeat.

The divided opposition helps Thatcher. On the current polls, showing the Tories in the 40s, Labor around 30 and the Alliance in the low- to mid-20s, she could double her last parliamentary majority of 48 seats without getting a majority of the popular vote.

Even more helpful to her is the low public regard for the opposition leaders. Roy Jenkins, the Alliance leader, has only a 36 percent confidence rating as a potential prime minister, and Michael Foot, the 69-year-old leader of Labor, described by The Economist as "a very old-fashioned political eccentric," suffers a devastating 19-71 negative rating. A poll taken three weeks ago showed Labor would be even with the Tories -- not 11 points behind, as it was then -- if the more moderate and dynamic Dennis Healey were leading it instead.

Labor is saddled not only with Foot but with a left-wing platform each of whose major planks, according to pollster Robert Worcester, is rejected by majority British opinion. Among other things, Labor is calling for withdrawal from the European Community, the ouster of U.S. bases, and the unilateral scrapping of the British nuclear deterrent -- plus a domestic program involving heavy government borrowing and higher taxes.

Reagan and the Republicans cannot count on the Democrats being equally stupid about their nominee or platform. But if the Democrats make the mistake of rerunning their 1972 campaign, the British example shows how far the Republicans might safely go in punishing them for it. The Tories ran full- page ads last weekend, claiming the Labor Party and Communist Party "manifestos" were identical on at least 11 points. "Like Your Manifesto, Comrade?" the headline read. "What was significant," said Conservative Party marketing director Christopher Lawson, "was that we got no complaints from anyone. That tells you something."

Another unique advantage Thatcher has is the Falklands War issue. The Tories looked to be a beaten party a year ago, running a humiliating third behind both Labor and the Alliance, before the Argentine invasion of the islands gave her a chance to show her mettle. "The Falklands transformed her," said Oxford political scientist David Butler. "It proved her toughness. Before that, when she called herself 'The Iron Lady,' she seemed like an actress on first night. She was easy to satirize. But after the Falklands, opposition speakers found they lost their audiences when they attacked her."

That lesson was proved again last week when Healey made the mistake of accusing Thatcher of having "gloried in the slaughter" of the Argentines. The public outcry forced an apology and hurt his party.

Reagan has had no chance as yet to chase foreigners off American soil. He has survived an assassination attempt, defied the air controllers' strike and stood up to Congress, welding his own reputation for toughness to a warmth of personality Thatcher has never managed to project. But as a national symbol, she has the edge.

She also enjoyed the advantage Reagan will not have of choosing her election date. June 9 was chosen when inflation fell to a 15-year low of 4 per cent (before heading up again in the fall, forecasts say), when industrial production and earnings turned up after three years of decline, and when optimism about the future was higher than ever in her term.

For all those reasons, Richard Wirthlin, Reagan's pollster, said last week, "I'm not sure that if she wins big, it necessarily bodes well for us. But I'm watching it very closely to see how her themes play."

One of the messages of greatest cheer to the GOP and of greatest gloom to the Democrats is that severe unemployment is not necessarily fatal to a conservative government.

One of Worcester's recent polls showed 69 per cent of the voters rated unemployment the country's leading problem, but even among them, Labor could muster no lead. Labor promises to give unemployment top priority, and cut it back to one million inside five years. Thatcher promises nothing, saying only that unemployment is "a lagging indicator" that will come along eventually as Britain's economic performance improves. She displays little sympathy for the jobless, responding to an unemployed seaman who fought in the Falklands with a severe reminder that "British vessels are 25 percent overmanned, compared to the Polish, and therefore cannot compete."

How have the Tories defused the issue? Partly by maintaining a safety net of payments for the older jobless, and promising training programs for the young -- who are the main objects of public sympathy. But mainly by persuading people that unemployment is beyond the reach of government policy, "Conservatives have convinced people over the last three or four years that it's in the stars," says political scientist Anthony King. "It's the result of a world recession, made worse here by long-standing failures of the British economy, which they are gradually putting right."

"The odd and disconcerting thing," said a Labor strategist, "is that when unemployment was of manageable proportions, people thought it was manageable. Now that it has grown hideously large, they have decided it is unmanageable -- by anyone." Indeed, a poll published Friday by The Guardian found that a plurality of voters said unemployment would "never" get back down to the 1979 level, under any party.

The same poll found less than one-third thought the Thatcher government mainly to blame for unemployment or believed that it was worse here than in most other industrialized countries -- although it is. That is no accident. Chris Lawson, the Tories' ad man, says "early on, we started delivering the message that if there were any easy answers, some government in some country would have found them. There aren't."

And the important lesson Thatcher is ready to teach is that if "a political wedge has been drawn between those in work and those out of work," as King says, the votes are with those working.

Worcester, who polls for the Labor Party, among other clients, says that even at current levels of joblessness, "only 8 per cent of the voting public is unemployed and only 23 per cent have a member of the family unemployed. Slightly more than one-quarter of those unemployed are voting Tory because "she's doing what's right for the country's long-term good." The 92 per cent who are not unemployed give her big margins.

Thatcher's campaign demonstrates just how many political dividends can be reaped from cutting inflation, as she has done by more than half since taking office. The Observer reported last Sunday that while unemployment is widely judged the country's most important problem, when voters were asked "what matters most to you and your family," keeping down inflation led reducing unemployment by a 56-38 margin.

And the Tories have a landslide 3-1 advantage over Labor as the best party to handle inflation -- an advantage Thatcher presses by constantly reminding voters that food prices went up four times as fast under the last Labor government and by charging that Labor's plan for deficit borrowing to stimulate the economy and reduce unemployment inevitably would mean a return to higher prices and higher interest rates.

While pressing this attack, the Tories have had to defend themselves from the same kind of charges Reagan regularly hears Democrats make about his cutbacks in popular domestic programs. As Reagan bought himself some immunity by agreeing early this year to a compromise that safeguards the Social Security system, so Thatcher has armored herself by increasing, not cutting back, funds and staff for the most popular part of the British welfare state, the National Health Service.

When Labor charges that she has "secret plans" for the second term to "force patients into private facilities run on a profit-making basis," she has the credibility to respond, "I have no more intention of dismantling the National Health Service than I have of dismantling Britain's defenses."

Although Thatcher's tax cuts, like Reagan's, have been tilted to the upper-income earners, the opposition has not been able to make "the fairness issue" a winner here. Even more than Republicans, Tories are seen as the party of the rich. But by cutting tax rates and encouraging capitalist dreams through such devices as selling 500,000 "council houses" (public housing units) to the tenants, Thatcher has expanded her following in the middle-class and held the allegiance of the skilled workers at the same level she enjoyed in her 1979 victory.

Indeed, she is showing how a conservative can gain votes by exploiting the public distaste for trade unions. It is a point Peter Hart is probably telling Democrats in general and Mondale in particular to contemplate, as they await the embrace by the AFL-CIO of a Democratic presidential contender.

Here, of course, the Labor Party and the labor movement have long been formally linked. Trade unions finance Labor and exercise major power in its decision-making. But trade unionists are a declining share of the electorate, and polls show Thatcher has a winning issue in the "reforms" aimed at giving individual union members an easier way to deny a portion of their dues going to the Labor Party. More broadly, to the extent that union wage demands and work rules are seen as a barrier to economic recovery, the partnership actually weakens the Labor Party's credibility as a provider of new jobs.

A bigger caution light to the Democrats comes from Labor's embrace of the disarmament movement and the rejection of nuclear weapons. Foot himself has long condemned nukes on moral grounds, and in recent years, the members of the growing Campaign for Nuclear Disarmament have become an important part of grass-roots Labor organizations, as anti-nuclear activists have in the Democratic Party at home.

But this campaign is proving that it is one thing to criticize the costs or effectiveness of particular weapons and something else to advocate unilateral disarmament. Majorities in Britain oppose the planned deployment here of U.S. cruise missiles and the Thatcher government's plan to spend $10 billion buying Trident II submarine-launched missiles.

But instead of focusing on these questions, where Tory voters themselves are split, Labor committed what Alliance leader David Owen called "an act of self-immolation." It called for the removal of American nuclear weapons and bases, and the scrapping, within five years, of Britain's own nuclear deterrent.

The effect has been ruinous. Less than one Briton in five supports that policy, and by a 3-1 margin, voters say Britain would be less safe if Labor came to power.

It also played directly into Thatcher's hands -- as any similar stratagem by the Democrats would help Reagan. In lines that Reagan could deliver as well as she did, Thatcher told a television interviewer last week that Britain needed her nukes because "bullies go for people who are weak. The alternative is surrender or capitulation. Surrender or capitulation! For Britain, never!"

And that raises what may be the most important point of all -- the way in which leaders like Thatcher or Reagan can set the terms of campaign debate by the character they create for themselves. For Thatcher, it is all summed up in her favorite adjective: "resolute". Like Reagan, she frames her arguments at the level of values, not just of policies: "self-reliance, personal responsibility, family loyalty, voluntary help to the less fortunate, those are what we stand for," she has said.

"Confidence, self-respect, integrity, determination, resolve," the Tory manifesto echoes. It is a document, as many have noted, that is remarkably scarce of specifics and devoid of stratagems for digging Britain out of its economic hole. Instead of a program, Conservatives have a new symbol for the campaign: the torch of freedom evoking the same spirit as "Chariots of Fire."

By keeping the debate at the level of fundamental values, Thatcher often has made her opponents seem picayunish, narrow and sectarian, when they promise to adjust this rate or change that regulation. That is especially true of Labor, whose platform outdoes even the Democrats' traditional solicitude for particular constituencies, even including a special pledge to look after those creatures "kept in zoos, circuses and safari parks."

By contrast, the Tory platform ends on a high note: "Under Conservative government, confidence is brushing aside pessimism at home. Abroad, Britain is regarded for the first time as a country with a great future as well as a great past. We mean to make that future a reality."

Peter Hart said he was struck by "the way Thatcher has defined the issue as the future vs. the past." With Foot as its leader, rambling on about the struggles of the 1940s and 1950s, Labor seems to be what Michael Barone has called the Democrats -- "the party of the status quo," or maybe of the past.

None of this proves, of course, that Reagan and the Republicans can win again by following the Thatcher model -- or even that she is immune from upset on Thursday. The Democrats have the possibility of playing one trump card that is not in Labor's hand. Whereas the turnout of voters in British election is consistently high, and does not vary much from one election to the next, the Democrats can expand the electorate. The success of Democratic registration and turnout drives among blacks, Hispanics and low- income whites in many local and state races since Reagan became president shows this is much more than a theoretical threat to Reagan and the Republicans.

But, equally, what Thatcher is doing here is more than a theoretical threat to the Democrats. Despite the rigors which Britons have endured the lest four years, she has turned the economic issue to her advantage. While re-election campaigns normally focus on the incumbent's record, Thatcher has managed to turn this election into a test of the nation's willingness to "stay the course."

She has contrived to shift the question from the wisdom and effectiveness of her own specific decisions and policies into the very different question of whether Britons will be as "resolute" as she is herself. And Reagan is capable of doing the same thing. Peter Hart said, "the distillation of what I heard from the voters in Britain was this: we must keep going. Thatcher is not perfect. But we can't go back to Labor. All the hard times we've gone through will go down the drain if Michael Foot wins."

Substitute Reagan for Thatcher and whatever Democrat you wish for Foot, and you will understand why Hart went home shaking his head.