NO INSTITUTION in American politics has changed as much in the past decade as the U.S. Senate: a dramatic switch in party control in 1981, marked movements in ideological balance through the 1970s and into the 1980s, major reform of its internal institutions, including the committee system and the budget process, and several important changes in leadership. And yet no comparable institution in American politics has been written about so little.

With its intrinsic powers, its institutional majesty, its colorful and powerful members, the Senate has consistently fascinated journalists, political scientists and other political mavens. But it has attracted few solid books explaining its internal workings and broader role. (The House of Representatives, with more members, more rules, more regularity, is easier to generalize about, and easier to get a handle on.) There have been definitive books about the postwar Senate -- William White's Citadel (1956) and Donald Matthews' U.S. Senators and Their World (1959) come to mind. And several interesting memoirs, such as Harry MacPherson's A Political Biography and James Buckley's If Men Were Angels, have shed some light on the institution. But all preceded the tumultuous era of change. The last good look at the Senate, journalist Bernard Ashbell's The Senate Nobody Knows, is now 8 years old.

Now comes a new and welcome entry into the field. James A. Miller, a young CBS producer, spent nearly two years working for Tennessee Senator Howard Baker just after he became majority leader in 1981. Before that, as a student of the late, legendary Professor Phillip Williams at Oxford, Miller had an opportunity to hone his skills as an acute observer of political institutions. While working in the Senate, Miller kept a journal. His book does not reproduce that journal, but adapts its observations to the task of describing the modern-day Senate. The result is not comprehensive or definitive, but is a very welcome and timely addition to the literature.

Miller takes a week -- specifically, the week of April 25, 1983 -- and follows it through the eyes and actions of several key actors, senators and staff. Miller's own participant observation is embellished by a lot of research and a lot of interviews. His centerpiece is then-majority leader Howard Baker, Miller's employer at the time and clearly the most important figure in the Senate. But Miller also focuses on Republican Senator Alan Simpson of Wyoming, Democratic senators Chris Dodd (Connecticut) and Frank Lautenberg (New Jersey) and several key staffers, including Jim Range of Baker's staff, Senate Budget Committee staff director Steve Bell, and Mary Jane Checchi, an aide to freshman Lautenberg.

During that week three years ago, several issues crowded the agenda. The struggle for a budget topped the list; the president's attempt to build support for his Central American policy followed, as did the effort to get a comprehensive immigration bill through the legislative labyrinth (Plus ca change. . . ). Miller takes us through the machinations on these and several peripheral policy battles, stopping from time to time to offer observations on the Senate, from its dependence on staff to its obsessions with television coverage. The format is a bit awkward, lacking in depth and continuity. But thanks to Miller's fine eye for detail, basic understanding of politics and political personalities, and an easygoing writing style, the book works. It provides a genuine feel for the hectic pace and lack of movement in the contemporary Senate -- the title, Running in Place, is perfect -- without displaying the contempt for Congress thais de rigueur in contemporary journalism. One emerges from this book frustrated over the petty ego trips and crass maneuvering in the Senate -- but convinced of the basic decency of the people and the institution.

Which is not to say that Running in Place is a whitewash. Miller provides an unvarnished and honest look at a legislative body which he says has "one foot in the past and one foot in the future, straddling eras and struggling to find an identity." Miller's account does not sugarcoat the roles or behavior of individuals. While one cannot come away from this book without liking and admiring Howard Baker, his portrait shows warts in the handling of staff and his own personal ambitions. Budget Committee staff director Steve Bell comes across as insensitive, hard-nosed, aggressive and egotistical -- an accurate portrayal of the traits that enabled Bell and his boss Pete Domenici to take on the White House in budget wars head-to-head for five years running.

Miller also offers a series of telling anecdotes involving freshmen Republicans that up to now have been only fodder for Capitol gossip mills. When New York's Senator Alphonse D'Amato learned that he was going to be assigned to the new Hart Office Building, he "took the news like an election defeat. Terrified that his constituents would think he was living in the lap of luxury if he moved into the new clubhouse, D'Amato devised a plan whereby the sergeant at arms would send the Capitol police to his office in the Dirksen building, and in front of a New York TV station crew, forcibly transport him, in his chair, to the new building. But the rules committee chairman Charles Mathias rejected the scheme, because "I didn't think it was appropriate for a United States senator to be manhandled by the police."

THE MULTITUDE of hazards to contemporary Congressional leadership emerges in another tale, in which Majority Leader Baker has to fend off a rambling and combative fellow Republican, Steve Symms of Idaho, on the Senate floor to protect the immigration bill; the Symms problem, it turns out, comes from a long, liquid lunch with his secretaries to celebrate Secretaries Week.

Baker greets the Symms problem with a deep sigh. Baker sighs a lot in this book, as when he finds his carefully planned Senate agenda disrupted by two junior Democrats' plan to call a secret session over Central America -- something he is powerless to stop -- waits patiently in an important Republican policy luncheon for freshman Republican Mack Mattingly to finish an interminable and pointless soliloquy about his encounter with the National Security Council staff, and tries to find some common ground in his GOP flock on the eternally nettlesome budget.

In the book -- as in the Senate -- the budget is omnipresent. In the Reagan (and Republican Senate) era, the budget dominates, acting as a metaphor for the frustrations of governing. One main reason for those frustrations emerges from another Miller anecdote, this one about the lengthy tug-of- war between Senate Republicans and Defense Secretary Caspar Weinberger over the defense budget. As Miller tells it (and my own sources have told it exactly the same way), a long and arduous series of negotiations between the White House and the Senate Republicans produces an agreement to work for a 7.5 percent increase in defense spending, compromised from the president's request for 10 percent. Everybody signed on but Weinberger, who held out stubbornly for 7.9 percent until the compromise ultimately fell apart. By the time Weinberger agreed to drop his bottom line by 4/10ths of one percent, the Senate had moved to a 5 percent hike, thumbing its collective nose in frustration at Weinberger's intransigence.

Clashes with the executive and lack of consensus on key issues are nothing new in the Senate; neither are the perennial headaches of juggling the demands and egos of 100 prima donnas. Many of the complaints voiced about the Senate, from inside and out, have been heard since the beginning of the Republic and reflect our own ambivalence about politics, politicians and checks and balances. But some elements, from the television age to the incredible congressional bureaucracy, are newer factors shaping the institution in the '80s. James Miller's interesting and insightful book helps put these factors into perspective, in a way that will enlighten both political junkies and college freshmen.