By Bill Lofy

University of Michigan Press. 224 pages.

One of the most joyful political careers of modern times came to an end three years ago tomorrow amid indelible sadness.

Sen. Paul Wellstone (D) was in the closing days of what looked likely to be a successful campaign for a third term representing Minnesota when he perished in a private-plane crash that also killed his wife, daughter, three aides and the two-man crew. In a horrible instant, a beguiling and wildly improbable political and human story was over.

Bill Lofy felt this tragedy more acutely than most. He was attending college in Wisconsin in 1991 when he became enamored with the crusading liberal who had just won an astonishing upset victory in the neighboring state. Lofy later went to work for Wellstone, serving as his traveling aide in the 1996 reelection campaign. He was traveling overseas as a graduate student when he saw the news of Wellstone's death on an airport television and immediately flew back to Minnesota.

Now Lofy has written a biography, "Paul Wellstone: The Life of a Passionate Progressive." The book is a capable and sometimes-compelling summary of the Wellstone story. Though written as a tribute, it is a clear-eyed one that reckons with the complexities of its subject.

I read the book from a particular vantage point. Wellstone was a professor of political science at Carleton College in Northfield, Minn., where I was a student. I never had Wellstone in class, but I saw plenty of him on campus and began a friendly, if sporadic, acquaintance that stretched over the last 20 years of his life.

When I first encountered Wellstone, he was the campus agitator, always gathering admiring students to go up to Minneapolis to protest the Honeywell Corp. (which manufactured cluster bombs for the military), down the road to Austin (on behalf of striking workers at the Hormel Foods Corp. meatpacking plant) or to the state Capitol in St. Paul to promote the nuclear freeze movement.

As a student, I was not a devotee, but even then watched Wellstone as a journalist. He left a vivid impression in rhetorical flight: the short professor in blue jeans, bouncing on his toes, arms flying about, his importuning words growing in passion and volume until he was nearly shouting. Wellstone always had his student supporters, but in those days they were dwindling. He was a campus hero during the protest years of the early 1970s, but a decade later, even a mostly liberal campus had settled into relative quiescence. Wellstone was widely regarded as an anachronistic figure -- even a faintly ridiculous one.

In 1982, he relied on his grass-roots supporters to gain the Democratic-Farmer-Labor nomination for the obscure job of state auditor, the keeper of the state government's fiscal accounts. He talked about nuclear peril and economic justice, and hoped voters would overlook his slim credentials and his admission that he was unable to read "graphs and charts and figures." Not surprisingly, he was routed.

It was a surprise -- it floored me, in any event -- when eight years later, Wellstone's underfunded grass-roots campaign ousted incumbent Republican Rudy Boschwitz and the professor moved to the U.S. Senate.

The best part of Lofy's book is the way he shows how this pattern of failure, self-correction and comeback was woven through Wellstone's life. He struggled as a student in Arlington and flirted with delinquency before athletics -- wrestling and cross-country running -- gave him direction. At Carleton, his preference for protest over rigorous academic work led to his firing -- a decision that was overturned by a campus protest. In the Senate, his self-righteous publicity stunts and inability to set priorities at first threatened to make him a laughingstock. Focusing his attention and modulating his voice, Wellstone became more effective and was liked even by Republicans such as Jesse Helms (N.C.) for his cheerful tenacity.

Lofy places Wellstone's wife, Sheila, prominently in his story. Wellstone was just 19 when they married, and she was by this account an indispensable anchor in his public life.

The author recognizes that his hero could be erratic. He could let enthusiasm outpace judgment, sometimes lost his temper with staff and was thin-skinned about press coverage (a point I can vouch for). But in cooler moments, he recognized his weaknesses and tried to compensate.

The great continuity in Wellstone's life was his commitment to people in distress and his belief in the power of political organizing. Lofy might have given a bit more attention to the ideological journey. In his early career, Wellstone was a radical who worshiped leftist organizer Saul Alinksy. In the Senate, Wellstone promoted himself as the natural heir to fellow Minnesotan Hubert H. Humphrey -- the kind of establishment liberal he once disdained.

The comparison was not just misplaced but unnecessary. As Lofy shows, in a capital of familiar types, Wellstone was an original.

Harris is The Washington Post's national political editor and author of "The Survivor: Bill Clinton in the White House."

Sen. Paul Wellstone (D-Minn.) died in a plane crash in 2002.