The United Mine Workers union was once described proudly by the late John L. Lewis as the "shock troops of the American labor movement." Now the UMW is simply in a state of shock.

The union that defied Presidents with impunity during Lewis' 40-year reign is paralyzed with internal dissension so intense that some industry and labor leaders are claiming it threatens the union's own hegemony in the coal fields.

The strife within the union is coming to a head - although probably not an end - in a bitter three-way race for top national offices of the 277,000 member union on June 14.

The voting will determine the holding power of the rank-and-file "reform" movement that took over the union under a pro-democracy, anti-corruption banner five years ago. But it is not expected to return stability to the mines or the miners union.

As evidence of the once militant union's already faltering grip in the mines, those who worry about its future point to:

Wave upon wave of wildcat walkouts, staged over the largely ineffectual protests of UMW leaders, that have resulted in an estimated loss of 20 million tons of mined coal and 3 million man-days of work over the past two years - prompting coal operators to question whether they should continue national contract bargaining.

The widely accepted likelihood that these rebellious local work stop-pages will lead to a full-fledged nationwide coal strike when the present national contract expires in December with serious implications for the nation's energy supplies as winter begins.

The apparent inability of the 80-year old UMW, with its Appalachian traditions and national contract priorities geared to the needs of Eastern miners, to organize workers in the expanding coal fields of the west.

A precipitious decline in the UMW's share of total coal production, down from 70 to 54 per cent in the last five years, and a resulting increase in production of coal by nonunion workers and members of other unions that are making inroads in the mines, including the Operating Engineers and Teamsters.

A dramatically changing work force whose average age has dropped from 48 to 34 in the past decade, producing a better educated, more independent breed of miner and, in the West miners who were not weaned on reverence for the UMW.

The irony is that the UMW is falling apart just as the coal industry faces a potential resurgence under a new national energy policy calling for massive increase in coal production, especially in the East, where the UMW has been entrenched for generations. President Carter's energy program envisions increasing annual coal production from roughly 650 million tons to 1 billion tons by 1985.

If the mines profit through higher production, prices and profits, so could the miners if they are in a position to push their claims, according to industry officials.

"The benefits of growth are there, and they're losing them," said Joseph P. Brennan, president of the Bituminous Coal Operators Association, the industry's chief bargaining group.

The coal will be mined, industry and administration officials agree. The only question, they say, is who will mine it.

It is in this context that UMW members are being asked to choose their leaders for the next five years - in a climate of unionized guerrilla warfare at the highest levels.

The reform minded team that five years ago toppled the autocratic regime of W.A. (Tony) Boyle - who is awaiting a new trial on charges of ordering the 1969 murder of UMW insurgent Joseph A. Yablonski, his wife and daughter - is now divided.

President Arnold R. Miller is being challenged by his former ally, Secretary-Treasurer Harry Patrick, as well as by Lee Roy Patterson, the candidate of the old-guard faction that backed Boyle in 1972.

Thus it is possible, even likely, that the UMW's much-ballyhooed experiment in union democracy will end in little more than a return to the old order - a victim of its own inexperience, weakness, excesses and divisions.

"It's a tragedy, an absolute tragedy," said Douglas A. Fraser, who is expected to be elected president of the United Auto Workers this week. Asked about the UMW in a recent interview, Fraser, a Miller sympathizer five years ago, said, "It's in disarray, it's gone to pieces, Miller just can't handle it . . . It's so sad because that union had a great history and it's just going to pieces."

Few blame Miller for all the union's troubles, noting that problems were inevitable for a union that changed, almost overnight, from one of the nation's most autocratic to one of its most democratic.

But Miller and his stewardship of the union are clearly the central issues in the campaign, which is already raging at a high pitch although there are few signs yet that the average miner is paying much attention.

Both Patrick and Patterson accuse Miller of inept, arbitrary and absentee leadership that threatens the union with ruin.

Likening himself to a Caesar surrounded by a whole host of Brutuses, Miller responds that his leadership has been thwarted by obstructionism from other union officers, including Patrick, Patterson and a majority of the union's 21-member international executive board, which at one point tried to oust Miller from office. Miller has reciprocated by routinely ignoring their actions. A week-long meeting of the officers and board last week resulted in a little more than a cross fire of political torpedoes from all camps.

Miller, 54, a black lung victim and third-generation West Virginia miner, was the compromise choice of the reformers in the 1972 court-ordered election. But nearly all the young reformers who accompanied Miller to the union headquarters at 15th and I Sts. NW have quit or were fired. More recently his five-member professional campaign staff quit. A common complaint was that Miller was impossible to get along with.

"He's a very ordinary man thrust into extraordinary circumstances," said a former aide. "He responded by running away from problems and blaming others for his own failures."

Stories about goings-on at the headquarters are now part of the Washington folklore. Once a door was removed from the office of a secretary whom Miller suspected of plotting against him. Patrick said Miller tried to freeze him out by turning off the heat in his office. The researchistaff has left and Miller says it isn't needed to negotiate the next contract.

Many of the disenchanted reformers are now hanging their hopes on Patrick, a stocky, articulate 46-year-old former West Virginia miner, although the extent of Patrick's support in the mines is uncertain. The third member of the successful 1972 ticket, Mike Trbovich, is backing Patterson.

Patterson, 42, a tough-talking former strip-miner from Kentucky who sits on the union's executive boad, campaigns on a we-told-you-so theme. He says he can no more be blamed for supporting Boyle than "all those people who voted for Richard Nixon" although he credits Boyle with running a smoother union than Miller does.

But Patterson pays backhanded tribute to some of the Miller-Patrick reforms, saying he would retain rank-and-file election of officers and contract ratification.

A key question is the popularity of the 1974 national coal contract, which the coal operators describe as the most expensive in their history, including a 29 per cent increase in wages, 71 per cent increase in benefit costs and 140 per cent increase in contributions to health and retirement funds. Patterson charges it was not good enough, with pension ambiguities that have caused current difficulties.

All three agree that union locals should have the right to strike at any time over grievances, a demand that operators say would only legitimate wildcat walkouts. The coal operators will demand more stability not less, said one industry official.

The seemingly irreconcilable nature of the impending clash was illustrated by two comments in West Virginia earlier this month. Speaking to the Bluefield CHamber of Commerce, BCOA's Brennan, describing labor relations in coal as "industrial anarchy on a grand scale," said wildcat strikes were threatening the whole pattern of collective bargaining in coal. Outside a UMW meeting in Morgantown, Ed Ryan, a militatn young Ohio miner, responded: "The company can do damn near anything it wants, so the right to strike is all we have."