The winner is the average wage-earner - the bread-truck driver, say, who pulls in $15,000 a year.

The losers are the more well-to-do - the highly paid engineer, the employer who hires him, and self-employed doctors and architects.

That's rough sort of box score on the Carter administration's plan for bailing out the Social Security system, a proposition that breaks sharply with tradition by introducing new financing mechanism. The heavy burden falls on the affluent - high-salaried workers, their bosses and the people who pay the biggest general income taxes.

Since its founding in the 1930s, Social Security has been funded by what is sometimes called the "50-50 formula." The workers and his or her boss have paid equal tax rates on the worker's wages. When more money has been needed, the tax has gone up for both.

Carter would break up that tandem in two ways: employers would pay more, and, temporarily, a big part of the revenues would come out of the Treasury's general income taxes.

The administration measures the impact by imagining a hypothetical employee who makes $10,873 next year and whose income rises to $14,125 by 1982. The employee's taxes are already going up under existing law, and by 1982 he or she will pay $890. If the administration met the current Social Security crisis in the conventional way, by raising the tax rate or the income base it's paid on the employee would pay an additional $77 by 1982. Carter's proposal, if Congress buys it, saves the worker that $77.

For the better-paid worker, making, say, $25,000 a year, the story is a little different. By 1982, he or she will pay $76 more because the amount of wages to be taxed will go up, in stages. But if the traditional path of raising taxes to match all deficits had been followed, he or she would be paying $663 more that year. The savings is $587.

So to help Social Security meet its short-range deficit, all employees would pay less in payroll taxes than they would if the administration had followed the usual pattern of raising taxes equally on employers and empooyees.

That leaves a proportionately larger share to be paid by employers. Carter proposes to take the lid off the amount of workers' earnings on which business is taxed. That lid now is $16,500.In 1979, employers would pay taxes on salaries up to $23,400. In 1980, it would go up to $37,500. By 1981, the employer would pay taxes on the total salary earned. Between 1978 and 1982, the higher employers' taxes would kick in about $30 billion - more than a third of the short-term deficit, the administration is trying to eliminate.

Many doctors, lawyers, architects and other professionals also would pay more during that period - about $1.2 billion more - because another section of Carter's proposal would increase their tax from 7 to 7.5 per cent. That would restore a ratio maintained from the early 1950s until changed in 1972 amendments.

The other break for the average wage-earner comes in the decision to tap general fund revenues for Social Security in a period when unemployment is high. Unlike the flat-rate payroll tax, income taxes are levied progressively: the affluent pay at a higher rate than the poor and middle-income worker. In effect, that move would take $14 billion of pressure off the payroll tax structure in the next five years.

Critics are saying that the savings to those of modest means is illusory. The businessman, they contend, will simply pass on his higher payroll costs to the consumer, and the worker's family will end up paying for the increase anyway. "The housewife will get it [the cost increase] when she goes to the supermarket," declared Rep. William M. Ketchum (R.-Calif.), a member of the House Ways and Means Social Security Subcommittee.

The administration's answer is that it ain't necessarily so. Health, Education and Welfare Secretary Joseph A. Califano Jr. told the subcommittee Tuesday that in a competitive business system some companies will pass the higher payroll costs on, some won't. Califano has said that corporations have plenty of profits to absort the tax increase. And besides, he points out, if the conventional method of raising tax rates and wage bases on both sides were followed, without tapping general revenus, business would end up having to pay $4 billion more than the plan calls for now.