Washington — Sierra Club director J. Michael McCloskey waves a sheaf of ''STOP ACID RAIN'' post cards in the air. The cards are a peculiar shade of pink, as if they were once red but have been sitting outside next to a coal-fired utility plant.
''We're hoping this will spread,'' says Mr. McCloskey with enthusiasm. ''We're hoping this will become a chain-letter-type deal.''
At the Sierra Club's rambling Capitol Hill digs, as in interest-group offices all across town, it's time to gear up for the election-year offensive. As the November contest approaches, lobbyists are planning to make pet issues more visible, and plotting how to win influence by delivering votes.
Sierra officials, for example, say acid rain is going to be at the center of their organizing efforts. Their other political activities range from providing a shrimp chef for a candidate's fund-raising dinner to helping Sierra Club members become delegates at the national conventions.
''We're going to be working hard in key states to make a difference in how the vote goes,'' says McCloskey, who with his horn-rimmed glasses and gray suit could pass for a Boston banker.
Founded in 1892, the Sierra Club is one of the oldest and strongest environmental groups in the United States. The environment as a cause, however, tends to attract more zeal than money, and Sierra is not rich by Washington interest-group standards.
The Sierra Club Political Action Committee, for instance, contributed about $ 230,000 to candidates in 1982. The PAC of the National Association of Realtors, the J. Paul Getty of lobbies, spent $2.3 million in the same period.
Sierra's effect on the '84 elections - and the political benefits it may reap in return - will thus depend on the effort it can muster, instead of cash. In this it is similar to dozens of often-liberal public-interest lobbies such as the Nuclear Weapons Freeze Campaign and the National Organization for Women.
''We have to use what we've got, which is people,'' says David Gardiner, Sierra's Washington, D.C., legislative director.
From 1980 to 1983, former Interior Secretary James G. Watt - the environmentalists' archfoe - helped keep the Sierra Club's people roused and ready for action. During that time, the group's membership doubled, to 365,000.
With Mr. Watt out of office, Sierra officials are hoping that acid rain will in effect take his place.
''This is the issue we think best symbolizes this administration's failure to come to grips with our environmental needs,'' director McCloskey says.
Environmentalists say pollutants from coal-burning Midwest power plants are causing acid rain to fall on the Eastern US. The White House contends that it's not yet clear who is causing the problem, and thus it won't back bills to make utilities install expensive cleanup equipment.
So the Sierra Club, in concert with the National Audubon Society and other environmental groups, is trying to stir up grass-roots concern. In hopes of flooding Congress with mail, the groups are distributing thousands of ''STOP ACID RAIN'' post cards to members and other interested parties.
The post cards have a dual purpose. As well as making the acid rain issue more visible, they help Sierra obtain the names of voters interested in environmental issues - the raw material of ''people power,'' Sierra's Gardiner says.
These lists of sympathizers will be an invaluable aid in one of Sierra's main political activities - helping favored congressional candidates.
So far this year, the Sierra Club has given its seal of approval to 45 candidates for the House or Senate. More endorsements are sure to come. In 1982, 180 politicians received the Sierra nod. (About two-thirds won.)
Not all endorsees will get environmentalist help in their campaigns. Some have safe seats; some have no chance. Others are running in major media markets, such as New York, where the Sierra Club can't make much difference.
And those that do receive aid don't get much of it in cash. Sierra this year plans to donate about $250,000 in cash or political services (such as canvassing) to candidates, political director Holly Schadler says.
But they will get another kind of political currency - volunteers to knock on doors, wave signs, and hold fund-raisers. In '82, New Mexico senatorial candidate Jeff Bingaman had 600 environmental workers, Ms. Schadler says; Sen. Robert Stafford (R) of Vermont had 150, plus Robert Redford radio commercials sponsored by the League of Conservation Voters.
''The senator said that his reelection was contingent on the help he got from environmentalists and educators,'' says Stafford aide Victor Maerki.
Rep. Les AuCoin (D) of Oregon, a vocal opponent of James Watt's mineral-leasing policies, is facing a tough battle this year and is already receiving environmentalists' organizing help.
''The Sierra Club is cosponsoring one of our largest fund-raisers - a $25 -a-head shrimp feed,'' says Kevin Smith, Mr. AuCoin's campaign manager. ''Their regional director is going to be chef.''
The Sierra Club, of course, is not doing this just for the sheer pleasure of participating in democracy.
Members hope their involvement in congressional campaigns (local chapters also work on local races) will keep friends from defeat, generate goodwill, and build contacts.
''The relationships that are built in a campaign can be very valuable later, in lobbying,'' says Ms. Schadler.
The Sierra Club is also involved in the presidential race, but in a rather novel way.
In conjunction with the League of Conservation Voters (LCV), Sierra taught many of its members how to get chosen as delegates to the national conventions.
In 14 states, Sierra or LCV operatives held seminars in political strategy, complete with Republican and Democratic officials explaining caucus procedures. About 100 card-carrying environmentalists were elected or chosen as presidential delegates this year, Ms. Schadler says; another 100 or so have pledged to participate in an environmental caucus.
Most of these people are Democrats. Two delegates on the Democratic Platform Committee, in fact, are Sierra Club members.
Environmentalists hope the Democratic platform will address three specific issues: acid rain; more cash for the Superfund toxic-waste cleanup program; and faster movement to protect wilderness areas.
For most of its 90-plus years of existence, the Sierra Club paid little attention to elections. For instance, 1982 was the first year it officially endorsed congressional candidates.
But involvement in campaigns is proving very popular among the rank and file, Sierra officials say. Each of Sierra's 53 chapters has its own SCCOPE (Sierra Club Committee on Political Education); 23 have their own PACs.
Local members can endorse and help people running for all types of local office. Ann Timberlake, head of Sierra's South Carolina chapter, says her group works for county council candidates, as well as those running for Congress.
''I think it's extremely beneficial,'' she says. ''It has helped our members have more realistic expectations about people in politics.''