When Ronald Wilson Reagan watches the events celebrating his second inaugural on Monday, he would appear to be master of all he surveys, the most dominant American political figure since Franklin D. Roosevelt.

He won reelection by a historic Electoral College landslide. He is credited with reversing the decline in public trust in the government in Washington, which had plummeted under his four predecessors from 69 percent in 1966 to 25 percent in 1980. Since he took office, public confidence in government, which he has denounced with such vigor -- and, ironically, with such political success -- has doubled.

Indeed, some credit Reagan with nothing less than rescuing what they saw as a presidency imperiled by the errors and ineptitude of his predecessors. Not the least irony of his 20-year anti- government crusade is that he is in a position to turn over a greatly strengthened presidency to his successor -- of whichever party he may be.

But more skeptical observers contend that it may be basically downhill for Reagan from here on in. Some argue that he peaked in his accomplishments two years ago and is at the peak of his popularity now.

One student of the presidency, Prof. Theodore Lowi of Cornell University, who takes a somewhat dyspeptic view of the post-FDR presidency, dismisses even this as Pollyanna-ish twaddle. Reagan is no more the master of the presidency than was any of his predecessors, Lowi contends in a forthcoming book, "The Personal President: Power Invested, Promise Unfilled." It will eat him alive, destroy him just as it has all the successors to FDR except Dwight D. Eisenhower, he says.

Lowi makes a technical exception for John F. Kennedy, who died tragically in mid-passage, but he notes that Kennedy had encountered the congressional stalemate that every other recent president has, that little of his legislative program had passed and that he was in political trouble in the South when he made his fatal trip to Dallas.

But for all the other winners of the White House, from Harry Truman on, "the presidency has been something of a disaster," Lowi says. "Each was retired from office and from politics by reason of unacceptability to his own party as well as to the public at large. . . . Reagan will go out in disgrace like the rest."

Lowi makes attainment of the most powerful office in the world -- and presumably the most coveted -- seem almost a fate worse than death. George McGovern, he notes, has had a better life, to say nothing of reputation, since 1972 than has Richard M. Nixon. He says the same of other losing presidential candidates, Barry M. Goldwater and Hubert H. Humphrey, and for that matter such Democratic primary losers to Jimmy Carter as Henry M. Jackson, Edmund S. Muskie and Edward M. Kennedy.

And the winners all ask for it, he says. As in Greek tragedy, they are principle players in their own downfall.

The reason for this is that since FDR the president has asked for and gotten so much power that he then labors under high -- and unattainable -- expectations.

"First, having given presidents maximum power to govern and all the help they have ever asked for, the public has rationally focused its expectations on them, counting on them to deliver on all the promises they explicitly made," he says. "Second . . . the American people . . . see the presidency as their own property. They have invested fully in it . . . and they now look for delivery."

Lowi's jaundiced view of the modern presidency is grounded in his view of how it came to be.

"In the 1930s we got the idea that Congress was out of date, that the world was too complicated for it," he says. "We downgraded Congress the same time the fascists in Europe did the parliamentary democracies. We all pleaded depression and war, and we assumed that our war, our military, was democratic and this made a strong executive seem good."

But Lowi may be too gloomy. He may be underestimating Reagan's political skill and luck -- and the fact that as a president who is regarded as a staunch conservative who believes in something and sticks with it, Reagan has a lot more opportunity despite being a lame duck than some think. Reagan's second term as governor of California was more productive than his first.

He has already put the budget and tax increase proposals back in Congress' court and will play the game of "The Devil Made Me Do It" that he does so well -- arguing that he sent the proposals he campaigned on to the Hill but the (Democratic) Congress forced tax increases and cuts in defense spending on him, if that happens.

It may be that he has a limited time "window" of six or eight or 10 months to get the budget through, but he has unlimited time and opportunity in foreign affairs, particularly in negotiating a nuclear arms control agreement. There also is a lot of support for a tax reform and simplification program.

As a conservative, Reagan holds the political high ground. He can make deals with the Soviets and never be vulnerable to accusations of selling the country out as a Democrat would be.

He could shoot himself in the foot politically by going after constitutional amendments prohibiting abortion and mandating a balanced budget and by trying to involve the government in school prayer. But don't bet on it.

Despite his reputation as an ideologue, he has made a career of being a pragmatic, flexible politician when need be. The fate of his second term and his judgment by the historians is still firmly in his hands.