James G. Watt became secretary of the interior just five months ago, a brisk, self-certain and acerbic westerner who pronounced almost immediately that his task was to "undo 50 years of bad government."

The words were not unlike the campaign rhetoric that also brought Watt's leader, Ronald Reagan, to the federal capital.

But no member of Reagan's Cabinet has taken the rhetoric so literally, moved so rapidly and abrasively to carry out what he considers the mandate of 1980 and rubbed so many wounds raw in trying to achieve his task, or, as the born-again custodian of one-fifth of the United States puts it his "crusade."

Five months later, after creating political stresses that rival the physical stresses wrenching at the San Andreas Fault, no member of the Reagan team with the possible exception of Secretary of State Alexander M. Haig Jr. has stirred quite so much unease among his allies and antagonism among his opponents.

Ironically, the Watt controversy appears to be causing Reagan the most trouble in the area where the heavy-handed interior secretary was expected to do the Republicans the most good -- the West.

The political trouble has led to increasing speculation that Watt, unless he pulls in his horns, might be the first top-level Reagan appointee to be on the skids. In the past month White House aides have begun passing the word that Watt's appeal there will wane when presidential thoughts begin turning to the 1984 elections.

In recent weeks Watt has been warned by the Republican chairman of California that his policies on off-shore oil drilling could be ruinous to the party's hopes of taking control of the president's home state in 1982.

A Harris Survey showed a startling turnaround in western political sentiment since the November elections. The poll, conducted in early June, showed Democrats with a 55-to-36 lead in the region they lost over-whelmingly last year.

The reason, according to Harris, was "dissatisfaction with the environmental and land policies" advocated by Watt and the new administration. eLouis Harris concluded the western dissatisfaction "could cost the Republicans dearly in the 1982 elections."

Western Democrats, decimated in 1980 by the very rhetoric Watt now is trying to put into practice, have become so emboldened by the belief he has gone too far that the party's western caucus has called for his resignation before "our region [is] spoiled and wasted."

Watt also is running into flak from more neutral western observers. The Los Angeles Times, the West's most powerful newspaper, has called editorially for Watt's replacement.

Environmentalists, who see Watt as almost a devil-figure antagonist bent on turning around decades of preservationist gains, have begun a mostly symbolic national recall move against the secretary.

A handful of pre-Reagan Republican activists from former Interior Department regimes also are beginning to sound off, giving Watt's opponents hope that this marks the final dissolution of the secretary's almost nonexistent political ties to traditional eastern establishment Republicans.

Nathaniel Reed, an assistant secretary of the interior under both Presidents Nixon and Ford, recently assaulted Watt as a "disaster" whose policies were "bankrupt and infantile."

On Capitol Hill, where Democrats are running for political cover on most of Reagan's efforts to "undo 50 years of bad government," opposition to the combative, provocative Watt is mounting quietly but so steadily some are speculating that he may be a point of vulnerability for an administration that is difficult to attack directly.

The Democrats, who have had trouble keeping their House majority intact against the administration's military and economic thrusts, are far from intimidated by Watt.

In House committees they have undercut Watt on his attempt to place a moratorium on parkland purchases, raised a storm over his plans to recognize the Office of Surface Mining, blocked his attempt to allow oil and gas exploration in a Montana wilderness area and refused to appropriate funds for controversial offshore oil drilling in northern California.

Rep. Morris K. Udall (D-Ariz), chairman of the House Interior Committee which stands between Watt and at least some of his revolutionary goals, says he is convinced "White House people are beginning to worry that this department is being run by a guy so far off the mainstream that he is going to get them into all kinds of trouble."

Udall and others speculate that the White House has told Watt to pull back, lie low and let the fires die down, much as Secretary Haig did after he became the lightning rod for early controversy in the Reagan administration.

Watt says he hasn't received any such word. Top White House aides also insist the president backs his interior secretary all the way. Asked recently whether Watt was accurately reflecting the president's views, White House chief of staff James A. Baker III answered with a flat and unequivocal: "Yes."

Watt clearly has strong supporters outside the White House, too. Many powerful western Republican senators (seven of the 15 committee chairmen in the new Senate are westerners) believe Watt is their savior in the Interior Department.

So does most of the resources industry, which has felt "locked out" of western coal fields and oil reserves throughout the energy crisis.

"We're deliriously happy," Carl E. Bagge, president of the National Coal Association, said at the beginning of the Watt revolution. And a joke quickly made the rounds of corporate suites: How much power does it take to stop a million environmentalists? One Wat.

Still, politics by showdown does not have a strong track record in political Washington. With many of his early and provocative policy thrusts faltering or under strong attack, even some of Watt's natural allies are beginning to wonder if can last long enough to implement the 1980 rhetoric that brought him back to Washington.

The confrontational nature of a man whose words, political approach and policies make one side deliriously happy and the other furious inevitably makes Watt a political lightning rod.

It raises the question whether Reagan misread his 1980 mandate in appointing an idelogue to head the Interior Department. Reagan, both as governor and president, has had the most political trouble when yielding to the ideological edge that brought him to political prominence.

The Interior Department, despite its low profile over the years, is ready-made for controversy.

At Interior, Watt has jurisdiction over more than 350 million acres of federal land, including much of the West's land area and most of some states such as Alaska and Nevada. It is out of federal land policies that the so-called Sagebrush Rebellion boiled up and helped Reagan sweep all the western states in 1980.

Watt has jurisdiction over national parks and wilderness areas as well as oil leases and strip mining. He deals with fish and wildlife, as well as reclamation, Indians and cattle-grazers, endangered species and dam-builders.

Watt's department, by definition, is schizophrenic, suffering a constant tug between preservation and exploitation of America's natural resources.

But many believe Watt is making a serious error in wagering that the success of 1980 campaign rhetoric about getting the government off the West's back means westerners also are willing to give up environmental gains made in recent years.

Until 20 years ago the Interior Department was mostly a sleepy overseer of resource development, a not-always benignly neglectful headmaster for the nation's Indians and a quiet caretaker for a collection of romantic national parks.

Barring a major scandal, such as the Teapot Dome episode during the Harding administration, the department generally stayed comfortably out of the limelight, especially in the East. It also stayed comfortabaly out of the second part of its schizophrenic job description -- environmental protection.

All that began to change in the '60s, with the rise of the environmental movement and the emergence of a string of conservation-minded secretaries beginning with Rep. Mo Udall's brother, Stewart. Udall was a Kennedy Democrat, but the environmental consciousness that he began remained through following administrations and, in fact, got some of its strongest propulsion under Richard M. Nixon.

When Reagan told angry western cattlemen and miners that he, too, was a "sagebrush rebel" who would get the Interior Department off their backs, few expected the environmental side of the department's dual personality to remain dominant. Even so, the appointment of Watt took both environmentalists and developers by surprise.

"When a new administration comes in, you expect change," says Mo Udall. "But you didn't expect them to go out and pick the most controversial, bombastic person they could find and put him in."

Watt does not deny that he is controversial and bombastic and predicts, a thin smile betraying the stuble sarcasm, that soon "the credibility of the critics will fall out and within a short time I'll be bland and uncontroversial."

But he seems to be closer to his view of the truth when he repeats the story about the meeting at which Reagan offered him the Cabinet job. Watt says he told the president-elect he planned to be so controversial Reagan eventually might find it necessary to fire him.

Reagan said that was the way he wanted it, assured him he would be fired if necessary and then added: "Sic 'em."

Watt was an ideological choice -- a man who was directing the pro-development Mountain States Legal Foundation at the time of his appointment, who had lawsuits pending against the department he was about to head, a man who had gone so far as to question the patriotism of the environmentalists in the Interior Department during the '60s and '70s.

And Watt, just as he took Reagan's campaign rhetoric more literally than others in the Cabinet, sought to move faster than other Reagan secretaries. He quickly moved to open up federal lands to resource development, pushed for a moratorium on park expansion, fired 50 Interior Department attorneys involved in enforcement of environmental standards, cleaned out all the old Carter hands so he could get "good men" in with him.

But it took more than that to put Watt in the hot seat. Many find Watt's words and methods just as troubling.

In an early congressional appearance after his 83-to-12 Senate confirmation, Watt, a religious fundamentalist, sent buzzes through Capitol Hill hallways with his answer to a philosophical question about his views on preserving natural resources for future generations.

"I do not know how many future generations we can count on before the Lord returns," the tall, angular westerner said, his eyes piercing through the thick lenses of his glasses. Watt later explained that he didn't know when the Millenium might be: "It's been 2,000 years since the last coming of Christ and it might be another 2,000 before the second coming." l

He set off other alarms with a speech before national-park concessionaries who were concerned about the possible banning of horses and motorized rafts from some parts of the Grand Canyon. He told of a four day raft trip he had taken through the canyon late last year. By the third day, he said, he was "praying" for the helicopters to come in and get him.

"I don't like to paddle and I don't like to walk," the custodian of the nation's great outdoors said in what he later conceded was an ill-advised attempt at humor.

The flamboyant words go on and on -- questions about whether evolution is the only possible explanation after hearing a geologisths rhapsodic description of the Colorado River taking millions of years to carve out the Grand Canyon, his statement that "my responsibility is to follow the Scriptures which call upon us to occupy the land until Jesus returns."

Watt sometimes gets angry when his words are played back at him. But he rarely denies them, insisting that he was misunderstood or the words were taken out of context.

After the controversy over the speech to the concessionaries, he explained away the paddling and walking line this way:

"I, man, I tell you it was a good speech. My timing was down fast. I said, 'Don't worry about that, the horses are a legitimate recreation experience; I don't like to walk or paddle,' and everybody laughs and laughs. So one phrase is taken out of context and then Dan Rather says we have a secretary that doesn't like the outdoors. It's an unfair charge, and I resent it. Do you sense that I resent it?"

Watt concedes that he became even more controversial than he had hoped in his first months at Interior. Looking back over the first months, Watt says, "Hindsight may prove that I didn't handle myself quite right in it and we'll see about that."

But he gives no sign of backing away from the powder keg he has created and that now makes him probably the most vulnerable of Reagan's Cabinet members. One potentially explosive action is his opening up oil leases off the northern coast of California.

This set of leases in four tracts ruled off-limits by the Carter administration caused the GOP chairman in the president's home state to warn that following Watt's lead could destroy the party's hopes of "recapturing the state senate and assembly as well as regaining the governor's office for the first time since President Reagan left that office in 1974."

In a blunt letter to Watt, the chairman Tirso del Junco, warned "the progress we are making can be severely hampered should our candidates be forced into supporting the decisions you have made" tentatively to reopen the four northern California tracts. Other leading California Republicans, including Sen. S.I. Hayakawa and Rep. Barry Goldwater, also have spoken out against the oil leasing.

Udall half-jokingly kidded Watt recently, saying the new interior secretary's idea of a wilderness area "is a parking lot without the yellow lines."

Watt and Udall both are westerners who grew up where the bleak land barely covers the greates coal reserves in the world, where eons ago the collision of huge land masses buried the last of the American oil pools three miles deep, where a storehouse of minerals needed to nourish a technological civilization remains just a prospector and a bulldozer away from the factories of the East.

Those two westerners now are powerful men in a far-distant town and they view the heritage they left through different prisms.

The showdown has not quite reached the point of the Shootout at the OK Corral, a battle which took place on Udall's Arizona home ground. But the conflict is approaching that kind of pitch, the kind that still could leave political blood in the streets of Washington with the fate of the West at stake.