The butchers, the bakers and the tool and die makers have them. So do the pro-lifers and the pro-choicers. So does the New Right and so, playing catch-up, does the Old Left.

Nearly every special-interest lobby in Washington has one. Business lobbies have hundreds, dominating the field as never before. People pushing causes have them, people pushing products have them, people pushing candidates have them.

Even people who deplore them have them.

What everyone's got these days is a Political Action Committee, the new sugar daddy of the American political system.

While the debate over them rages, PACs proliferate. The Federal Election Commission now counts 3,115 political action committees, nearly five times as many as in 1974 and an increase of 350 in just the past year.

In the decade since they were created by Congress, PACs have rearranged the channels through which money flows into politics and may substantially alter the political process itself.

In the bad old days, political funds came from a small number of large contributions. That system bred scandal and fell into severe disrepute with the Watergate revelations.

The election finance reforms of the 1970s put limits on the amounts any one contributor could give but provided a vehicle--a loophole to critics--to circumvent the new spending restrictions: the political action committee.

Federal law limits direct PAC contributions to $5,000 to each candidate for each election, primary and general, but there is no limit on the number of PACs that can be formed--or on their independent expenditures on campaigns. Independent expenditures are those made without the knowledge of or consultation with the candidate or his managers.

To their critics, PACs are a remedy as pernicious as the disease. Rep. David R. Obey (D-Wis.), noting that PACs now are the source of nearly 25 percent of all the money raised by congressional candidates, says their initials ought to stand for "Pack the American Congress."

PAC money often is given with a specific legislative objective in mind, the critics say. They contend that PAC money weakens the influence of the political parties and individual contributors while strengthening powerful special interests.

Rep. Jim Leach (R-Iowa), who has introduced a bill limiting the total amount an individual candidate can accept from PACs, warns that labor and business PACs are "girding for future Armageddons--political campaigns that in quantum magnitudes are likely to be more expensive than Americans have ever experienced."

"If this trend toward more expensive races and thus heavier financial obligations for candidates is not curbed, individuals elected to the Congress will increasingly become indebted to either big business or big labor," Leach says. "Congress will become a legislative body where the small businessman, the farmer, the worker, and ordinary citizens are only secondarily represented."

He charges that the middle-class tax burden is heavier and inflation is higher because of the tax breaks and federal programs and benefits of the rich and powerful.

Leach also argues that huge PAC contributions will "Europeanize" the political parties, that is, polarize them, with business PACs supporting the Republicans, labor and liberal groups contributing to the Democrats.

The critics also charge that heavy PAC contributions scare out potential candidates who oppose the PACs and their champions and that they have made instant entrenched incumbents out of freshmen such as Rep. Jack Fields (R-Tex.) who are their fortunate recipients.

Leach, Reps. Dan Glickman (D-Kan.) and Mike Synar (D-Okla.) have introduced a bill that would limit total PAC contributions to $75,000 for an individual House candidate. It establishes a formula based on each state's population to limit contributions to individual Senate candidates.

PAC defenders argue that they strengthen the political process by broadening the base of participation.

Rep. Bill Frenzel (R-Minn.) argues that PACs "increase individual participation in the political system," multiply the effectiveness of small donors who average $15 to $20 each, offset the influence of organized labor, and "provide the potential to balance the inordinate advantages of incumbency." He argues that the very growth of PACs "takes a little sting out of saying certain people or certain groups are controlling the government."

Fred Wertheimer, president of Common Cause, counters that the so-called canceling-out phenomenon often doesn't occur.

"Who is on the other side of an issue from the realtors or the doctors?" he asks, citing two of the best financed association PACs. "Not the auto dealers. They've got their own PACs and they're out lobbying their own issues."

The great bulk of PAC money goes to congressional candidates, who, unlike presidential contenders, are not eligible for public campaign financing. PACs gave some $55 million directly to congressional candidates in 1980, with the contributions going to incumbents over challengers by a ratio of more than 2 to 1 and with Democrats favored over Republicans by a narrow margin.

They raised $81 million in 1981 and this year it could be as much as $100 million.

But not all PAC money goes directly to candidates. A growing amount--about $14 million in 1980, mostly by conservative PACs--is spent "independently," generally in attacking the opponents of candidates the PACs support.

PACs come in all shapes, sizes and ideological flavors. Here is a rundown of the different categories:

The Candidate PAC. For most of the 1970s while he was running for president, Ronald Reagan used a PAC, Citizens For The Republic, to build his political base. The CFTR raised money, through direct mail and other techniques, for Republican congressional candidates and Reagan's travels on their--and his own--behalf. Today, Sen. Edward M. Kennedy and former vice president Walter F. Mondale, two leading prospects for the 1984 Democratic presidential nomination, have similar PACs for the same purpose.

Business PACs. Business groups typically form PACs to collect legislative rather than political IOUs. One of the most energetic corporate apostles of the PAC movement, Justin Dart, a close friend of Reagan's and chairman of Dart Industries, noted: "Talking to politicians is fine, but with a little money they hear you better."

After a slow start, the business community jumped into forming PACs with a vengeance. In 1980, there were 1,835 business and trade association PACs, a four-fold increase over 1974. Over the same time, the number of labor PACs grew by only 50 percent. There now are about four times as many business committees as labor.

The growth of PACs is a classic case study in the Law of Unintended Consequences.

Organized labor was the prime mover behind the legislation that created PACs, which was written in 1971 and amended in 1974. At the time, unions were the chief conduits of institutional money into politics, and they thought they were tailoring a system, based on aggregating small voluntary contributions from a large number of members, guaranteed to preserve that dominance.

Instead, business and professional groups quickly discovered they, too, could raise money in small bites, and since they were drawing from a more well-heeled base--corporate managers, doctors, dentists, car dealers, realtors, etc.--they could raise more of it. Result: in 1980, the total business PAC contribution to federal candidates was more than double that of labor's.

Because business typically gives with a lobbying purpose, it tends to favor incumbents heavily over challengers. In 1980, however, there were the beginnings of a counter-trend; some business PACs, notably those in the oil industry, became much more aggressive in contributing to challengers, on the theory that the only way to get what they wanted from Congress was to change Congress.

* Labor PACs. Their growth in numbers and contributions may be far less dramatic that those of business, but they still lead the parade in a different form of candidate assistance: in-kind services.

Labor has long been effective in using its manpower and internal communications network on behalf of friendly candidates. Labor also is far more partisan about its giving than business. More than 90 cents of every labor dollar goes to Democrats, while just over 60 cents of every business dollar goes to Republicans.

* Ideological PACs. Far and away the two richest PACs in 1980 were two conservative ideological groups, the National Congressional Club, founded by Sen. Jesse Helms (R-N.C.), which raised $7.9 million, and the National Conservative Political Action Committee, which raised $7.6 million.

They used their money mostly for independent expenditures on behalf of--or against--given candidates.

Liberal Democratic groups are trying to catch up with the conservatives. One formed last year is the Progressive Political Action Committee, ProPAC, the liberal equivalent to NCPAC. It has targeted conservative incumbent senators such as Helms, Orrin G. Hatch (R-Utah) and Harrison H. Schmitt (R-N.M.), and is running negative ads against them much as NCPAC has attacked liberals.