IT SEEMS OBVIOUS at first glance that there is a difference between educating people about public issues and trying to influence how they vote. But the more you examine that distinction, the more difficult it becomes to define. For example, is an organization that has taken a stand on busing trying to educate or to influence when it tells its members what candidates for public office think about busing? That might not be worth thinking about except for this: The Internal Revenue Service has suddenly made the definition a matter of life or death for tax-exempt organizations.

Those organizations cannot send questionnaires to political candidates and publish their response on issues about which the organization is concerned, the IRS ruled, for the responses "can reasonably be expected on influence voters." Since the organizations are barred by Congress from participating in political campaigns "on behalf of any candidate for public office," they can thus lose their tax-exempt status. That would mean that contributions to them would no longer be deductible on federal income tax-returns.

The ruling is an abrupt change from past practice. Tax experts, with at least the acquiescence of the IRS, have said for many years that tax-exempt groups could use political questionnaires so long as they were non-partisan. That meant the questionnaires went to all candidates, and the response were published without editorial comment. The new ruling came, it appears, when an environmental group seeking tax-exempt status said it intended to send questionnaires on environmental issues and publish the answers. It was told it couldn't.

The logic of the ruling is easy to follow when it involves a single-issue organization. Presumably, a survey of candidates on air pollution, by a group created to educate the public solely about air pollution, would influence the votes of its members, as well as educate them. But when a multi-issue organization, such as the League of Women Voters, surveys candidates on many issues, is it educating or influencing? The tax experts say the league's annual questionnaires must disappear under the ruling. Yet we suspect few of the people who have used its questionnaires to inform themselves about local candidates have any idea of what the league's position is on the subjects involved.

The government encourages (through tax exemptions) organizations that inform the public about the substance of public issues. But the IRS ruling means the information such organizations provide must stop short of their greatest practical usefulness: how candidates stand on those issues. That kind of line-drawing between educating and influencing seems too fuzzy to survive. The IRS ought to stick with its old position, which drew the line at partisan participation.