MENTION touching social security at almost any time and official Washington cranks up into a tizzy. Mention it in an election year - as Treasury Secretary Donald Regan did this week - and the opposition pounces.
The public can observe the transparent political opportunism in Democratic rejoinders such as House Speaker Tip O'Neill's ''In their hearts they definitely want to strike at that fund,'' or Walter Mondale's ''These Republicans can't keep their hands off social security.''
It would be too bad to make social security - a system that paid out $170 billion to 36 million people last year - taboo in the critical months of national policy debate.
The system is a current issue in at least three ways - the long-term solvency of the fund, the program's role in reducing federal deficits, and to what degree the program should benefit better-off recipients. The solvency of the trust fund that pays out benefits was supposedly assured by Congress a year ago, although Mr. Regan has stirred up doubts once again.
At the moment there is no discussion of social security alterations in connection with this year's budget deficit exercise under way in Washington. Last year, a cost-of-living adjustment was postponed for six months, from July to January. And new rules required recipients earning over $25,000 to pay tax on half their social security benefits. There was no hue and cry over these changes. The economy generally was improving. And advocates for recipients realized that the deficit-reduction package was heavier on the tax increase side than on the benefit reduction side.
There's a basic argument about how to view the social security trust fund itself. By creating a large surplus in the fund, through benefit reductions, some say, the fund in effect can ''lend'' to the government: As payroll taxes are reduced, other taxes can be raised. But a dollar for deficit reduction is a dollar from trust-fund solvency.
In 1985, social security most certainly should be looked at again, whichever party wins the White House.
Restructuring the benefit formula for social security takes a long time to have an impact, since it affects age groups entering the system. So some analysts suggest taking off a couple of percentage points from the yearly cost of living adjustments - from 6 percent to 4 percent - for two or three years to get large sums for federal spending relief. Or they would end indexing for dependents' benefits.
Those who think benefits may needlessly be going to people who are well off may seek higher taxation rather than try to vary benefits by income level: A direct ''means test,'' when employees have already paid into the fund with after-tax income, would be unfair.
However high Washington's political risk in discussing social security is now , the responsibility for action in 1985 may prove even higher.