Sen. Ernest F. Hollings (D-S.C.) voted for airline deregulation two years ago, only to find that deregulated airlines are flying South Carolinians from Charleston to Washington by way of Atlanta.

When a bill to relax federal regulation of the trucking industry came before the Senate Commerce Committee recently, Hollings led the opposition to it. He is now, Hollings told his colleagues, a "born-again regulator."

Sen. Russell B. Long (D-La.) says he wants to "bring back the golden days of the railroads," but not, he emphasizes, at the expense of soaring rates for the transportation of Wyoming coal to Louisiana's electrical generators.

Long is proposing an amendment to pending railroad deregulation legislation that is aimed at keeping down coal hauling rates, pitting the utilities against the railroads in a lobbying tug-of-war that could shatter the fragile consensus in favor of the deregulation bill.

There are just two reflections of the Realpolitik of deregulation on Capitol Hill, where grand schemes for revamping whole industries can hinge on things such as South Carolina airline schedules or the cost of a lump of coal in the nation's oil belt.

"Everyong wants 'meaningful reform,' said a legislative aide, "so long as his own state doesn't lose anything."

Similarly, powerful economic interests -- railroads, truckers, shippers, manufacturers, retailers, farmers, energy producers and users -- share big stakes in the fight over deregulation but tend to interpret "reform" differently, mainly in line with their own profit-and-loss balance sheet.

Moreover, the public interest can be hard to identify when it boils down to a healthy rail system vs. reasonable utility rates -- or, as cynics suggest, a choice between robber barons and oil profiteers.

It is in this atmosphere that legislation to revitalize the nation's railroad system by relaxing nearly a century of government regulation of rates and service will come before the Senate e, perhaps next week.

The rail bill will be followed by legislation to open the trucking industry to more competition, a measure expected to hit the Senate floor later this spring.

Both bills are scaled-back versions of more sweeping deregulation legislation proposed earlier by the Carter administration. which, despite the problems of communities like Charleston, was pleased enough with airline deregulation to advocate virtual elimination of controls on rails and trucking.

The Interstate Commerce Commission, reshaped in its regulatory approach by administration prodding and appointments, has already relaxed many rail and trucking restrictions. The legislation would take deregulation a step further, although not as far as the administration wanted.

Even in their modified form, the pending Senate bills would affect nearly everything that moves in the American economy, with billions of dollars at stake for producers and consumers as well as the transportation systems that link them.

The problem is that there are winners as well as losers under government regulation, a system that has grown so complex that whole industries -- and public service systems -- have tailored themselves to its demands.

Freeing American industry from the shackles of regulation has become a political fetish in Congress, involving enterprises ranging from banks to funeral homes and television advertising for children as well as transportation.

But the consequences of unfettered capitalism can cut unevenly and in unintended ways. Hollingss and Long are not alone in flinching.

In the case of trucking, regulation in the form of market entry restrictions and fixed prices has shielded the industry from competition. As a result, major regulated trucking companies, backed by the powerful International Brotherhood of Teamsters, have fought deregulation while many shippers, farm interests and consumer groups have lobbied for it.

The trucking deregulation bill, as drafted by Senate Commerce Committee Chairman Howard W. Cannon (D-Nev.) and ranking minority member Bob Packwood (R-Ore.), would make it easier for newcomers to break into the industry. It would also limit the current practice of industry price fixing, provide greater latitude for individual companies to set their own rates and end rate regulation for fresh and processed foods.

In the case of the railroads, the industry claimed it has been strangled rather than shielded by regulation and has lobbied for sweeping deregulation. In turn, many rail shippers, especially so-called "captive" shippers that are heavily if not totally dependent on rails for movement of their goods, feared the potential fallout from the kind of deregulation the railroads were seeking.

The committee-approved bill fell considerably short of total deregulation and contained a few special interest sweeteners, such as protection for the grain industry from peak-season rate escalation and favored treatment for shipment of recycleable goods. It also skirted some highly controversial points for railroads and shippers.

But it was a compromise that most parties appeared willing to try to live with. And, with a 14-to-0 vote from the Commcerce Committee, it appeared headed for smooth passage in the Senate -- until Long, one of the Senate's most influential members, swung into action.

Shortly before Congress adjourned last year, Long served notice that he would push for a "presumptive cap" on rail rates, beyond which the railroads would have to prove their need for a rate increase to the ICC.

Long's proposal is aimed at curbing the already soaring rail rates for long-distance coal-hauling, rates that are likely to rise even further as conversion to coal accelerates. But the railroads point out that it would affect all commodities. And it would reverse the burden-of-proof rule that has prevailed for shippers opposing rail rate increases since 1887, they note, thereby increasing the vise of regulation rather than loosening it.

The problem of Louisiana and other oil-rich Gulf states is that they, like everyone else, are being forced to use more coal to help reduce the nation's oil consumption and thereby its dependence on the Organization of Petroleum Exporting Countries. The problem is intensified by these states' distance from their only possible coal market, more than 1,400 rail miles away in Wyoming and Montana.

In stating his case for the rate cap, Long cited the case of a Louisiana electrical cooperative that paid $32.17 a ton for coal that cost $8.25 in Wyoming, with transportation accounting for twice the actual value of the coal.

"My goal is to find relief for beleagured consumers in Louisiana and across the nation who are continuing a costly transition from oil and gas to coal . . . I do not believe we can make an orderly transition to coal by allowing the railroads to go absolutely hog wild in the rates they charge on this captive commodity," said Long.

Things have already gotten so out of hand, Long continued, that utilities in some states are looking to Poland, South Africa and Australia for coal that is cheaper than rail-borne American coal.

In addition to utilities' support for Long's amendment, other rail users have climbed aboard demanding equal treatment and effectively shutting off any chance of restricting the rate cap to coal.

While the outlook for Long's amendment is uncertain, deregulation advocates -- including Cannon, the railraods and the administration -- are taking it seriously enough to retrench a bit. They are pushing a Cannon-drafted substitute to provide more rate protection for captive shippers but not as much as Long wants. If Cannon fails and Long succeeds, the American Association of Railroads, the industry's lobbying group, would oppose the bill, an AAR spokesman has said.

"Deregulation is such a buzz word in Congress that the bill might well pass even with Long's amendment," said a pro-deregulation sources. "But it wouldn't be deregulation anymore."