BY SENDING OUT "ballots" soliciting opinions on various possible changes in Social Security, the National Republican Congressional Committee has provided new grist for the Democrats' mill. The ballots, part of a fund-raising questionnaire, ask voters to express a choice among three options, two of which would result in large benefit reductions to both current and future beneficiaries.

Such a questionnaire should not be confused with a serious statement of party policies. The accompanying letter, moreover, is correct in saying that people ought to give some hard thought to the subject before Congress decides how best to shore up Social Security's shaky finances. Understanding what's behind some of the committee's options isn't a bad way to start.

The first choice offered is to make Social Security voluntary. That's not a serious proposal for a very practical reason: if many workers opted out, benefits to current retirees would have to be sharply reduced, since payroll taxes collected from current workers are used to cover benefits to current retirees. Making Social Security voluntary would also destroy its primary function of providing all workers with the convenience, security and efficiency of a universal pension plan.

If Social Security were voluntary, it wouldn't be the rich who would most likely opt out -- payroll taxes aren't a big burden on high salaries, and you can't buy the kind of protection against inflation and early disability that Social Security offers for a comparable price. But many young people who find themselves hard-pressed to buy a home, educate children or help aging parents might choose to avoid the relatively large slice that payroll taxes take from moderate wages. In time they -- and their children -- would come to regret that choice.

The second option would remove the "welfare" elements from Social Security. This option drew the most favorable votes, perhaps because the people polled thought -- mistakenly -- that welfare programs for the destitute are funded from payroll taxes. But Social Security does incorporate welfare elements in the sense that benefits paid are not strictly related to prior contributions. The most familiar example is the weighted benefit formula that gives chronically low-wage workers a higher return on their contributions. Higher initial benefits for the poor are partly justified on strictly actuarial grounds -- lower income people tend not to live as long -- but the notion of ensuring a reasonably decent old age for people who have worked hard for little has always been part of the social insurance concept.

Most Social Security "welfare" benefits, however, aren't reserved for the poor. For example, the automatic adjustment of benefits for inflation means that, in periods of high inflation, all retirees are ensured of benefits that the most prudent investment couldn't guarantee. Other big welfare items are the substantial benefits paid to spouses and children of retirees -- workers pay no additional taxes for this coverage. The second option would cut out all such benefits before the worker dies.

That leaves option 3 -- leaving the basic system intact but adjusting taxes and benefits modestly and gradually to keep the system on a prudent course. That still leaves plenty of room for debate, but it gets our vote for a good starting assumption.