In the annals of campaign finance reform, a medium-sized lobbying group, the National Asphalt Pavement Association, has carved itself a small but potentially telling niche.

After six years of funneling ever-increasing sums into congressional campaigns, the NAPA decided to dismantle its political action committee and get out of the business of bankrolling candidates.

"The public perception of special interests controlling the Congress . . . that a congressman's vote can be purchased or rented threatens the very fabric of our government," the group's president wrote members of Congress last month.

The conscience pangs of one PAC out of about 3,400 do not a movement make, yet there are other storm clouds on the political horizon for the ubiquitous and fast-growing PACs, which provided about one-third of the money raised by the congressional winners of 1982.

Three Democratic presidential hopefuls, former vice president Walter F. Mondale, Sen. Gary Hart (Colo.) and former Florida governor Reubin Askew, announced recently that they will take no PAC money. This is as much a symbolic as substantive gesture because PACs play a smaller role in financing presidential campaigns, but there are signs that other politicians are ready to take their cues from the presidential candidates.

More and more members of Congress are openly expressing their fears of a political financing system that excites the strong suspicion--and possibly the reality--that the special interests that organize PACs get favored treatment from the legislators whose campaigns they underwrite.

"When these political action committees give money, they expect something in return other than good government," said Sen. Robert J. Dole (R-Kan.).

"I'm scared," said Rep. Barber B. Conable (R-N.Y.). "These new PACs not only buy incumbents but affect legislation."

"There has been too much discussion around here about how what we do in the House and on our committees is going to affect our ability to raise money," said Rep. James M. Shannon (D-Mass.). "I mean, people aren't embarrassed about saying this anymore."

Ideas for offsetting the increasing power of the PACs include federal financing of Senate and House elections, limits on the totals that a candidate can receive from political action committees, increases in the limits on contributions that individuals and the political parties can make to candidates, and tax credits for individual political contributions.

Not since Watergate has there been such a clamor for reform of the nation's campaign financing laws--themselves reforms that made the PAC explosion possible--but it does not mean that more "reform" will follow.

But the reformers are haunted by the fear that, whatever reforms they enact, the special interests will just find new ways to put their money and influence into the system as they did with the PACs. The asphalt-pavement association decision does not mean that members of the association are going to contribute any less independently.

Indeed, even the most ardent proponents of limiting the role of the PACs doubt they can steer any comprehensive bill through the 98th Congress.

"I would be surprised if the House doesn't pass a bill this session, but I'd be just as surprised if the Senate does," said David R. Obey (D-Wis.).

"I see this as a two-Congress fight," agreed Fred Wertheimer, president of Common Cause.

The modesty of their timetables is a bow to the complexity of their task. Fixing campaign finance laws has always been a bit like mending an old mattress; push down the springs one place and they pop out somewhere else.

The "reform" laws of the early 1970s that put limits on what individuals could contribute to federal candidates also enhanced the role of PACs, which pool the contributions of many small givers--corporate employes, rank-and-file union members, advocates of the same ideology or cause.

The big individual donor was replaced by the big group solicitor, which critics say is more corrosive because the PACs generally have a more specific legislative agenda than the Stewart Motts or the Clement Stones.

If PACs were the only perceived problem in financing federal campaigns, it would probably not be too difficult to fashion a politically acceptable way to limit their influence. But there are other complications:

* Since the Supreme Court ruled in Buckley v. Valeo (1976) that it was unconstitutional to limit what an individual or his family could invest in his own campaign, the phenomenon of self-financed millionaire candidates has grown. This raises a question of equity: If you restrict the access of candidates to PAC money, or other forms of funding, doesn't this add to the edge that the wealthy candidate already enjoys?

* The court also ruled that it is unconstitutional to limit what a PAC can spend on behalf of or in opposition to a congressional candidate, as long as the money is not a direct contribution, i.e., an independent expenditure.

Thus, any new limits on what PACs can give directly to candidates--which is now $5,000 per candidate per campaign, with no total limit on what a candidate can accept in a given campaign from all PACs--would likely push more PAC money into independent expenditures. Such expenditures are widely criticized because they avoid political accountability.

Given these considerations, Obey has concluded that a more comprehensive approach is needed--a voluntary, partial public financing of congressional elections.

His bill would impose an aggregate limit on what candidates could receive from all PACs.

It also would offer a dollar-for-dollar match of federal funds for any candidate who raises money from small, individual donors and agrees to an overall campaign spending cap. If a wealthy candidate chooses to forgo the cap and matching funds, his opponent would be entitled to a 2-for-1 dollar match.

To deal with independent expenditures, particularly by the "attack" PACs, such as the National Conservative Political Action Committee, which run negative ads against targeted candidates, the Obey bill would provide extra public funds and/or free broadcast response time for targets of such ads.

Obey has heard time and again that all his bill would do is force special-interest money to find new ports of entry into the system.

And the apparently high-minded intentions of the National Asphalt Pavement Association are instructive. Although it plans to dismantle its PAC, it will encourage its 650 members to continue investing in the political process on their own.

NAPA will continue to recommend where the money should go and, according to chief lobbyist Robert Busha, it doesn't think its clout will be reduced by the change. The net result of limiting the role of PACs could be that special-interest money flows just as freely, but less visibly.

Obey is undeterred.

"To make an argument against reform on the grounds that we'll only create new problems that have to be addressed later is sort of like saying, don't treat a cancer now because the patient will just live long enough to develop heart problems," he said.

"I don't compare this bill to God in his heaven, I compare it to what we're dealing with now. Members feel almost devoured by the financial pressures of the existing system, and they feel personally demeaned by it."

If Obey's comprehensive approach meets the same conservative resistance that has befallen previous efforts to get Congress to provide for public financing of its own campaigns, there are halfway steps that will be pushed.

Rep. Matthew F. McHugh (D-N.Y.), chairman of the Democratic Study Group and a key ally of Obey's, is intrigued by a bill that would increase tax credits available to individual donors.

Currently, there is a 50-percent tax credit for all donations to federal candidates, up to $50 ($100 on a joint return). McHugh would like a 75 percent or 100 percent credit and have the ceiling doubled, thereby making it painless for the individual donor to get into the political money game.

Rep. Bill Frenzel (R-Minn.) is a staunch defender of the PACs, but he is sympathetic to the criticism that the current system favors special-interest groups over general-interest ones. He has introduced a bill that would raise the limits on what individuals can give to parties and parties can give to candidates. The bill will be especially popular with Republicans, whose party raises far more money than the Democrats.

Congress has 535 "experts" on campaign finance laws, and there is no shortage of other ideas about how to fix the system, from the imposing limits on political advertising as a way to cut down costs, to creating a blind trust that would keep a candidate (and the public) from knowing which PACs gave how much to whom.

Obey is hoping to keep the dialogue alive, and senses that sooner or later, for all the obstacles, his public-financing approach will be embraced as the only sensible answer. "PACs became a campaign issue for the first time in 1982," he says. "If you're a congressman, it's going to be easier to explain to your constituents why you voted for public financing than why you voted against it."