Keith Prouty lived to be 81, but if you ask anyone, he was always a kid.

He took piano lessons with his children to support them in what otherwise might seem a chore. At end-of-term recitals, he'd get lost on the keys, then delight the audience with a cry of "Oh, phooey." That would relax the young pianists, as if to say: Even daddies mess up.

In his Bethesda neighborhood, he was the bespectacled, apple-cheeked adult who participated in kids' baseball and football games. He also patiently let youngsters line up time and again for thumb rides, when they would grab hold of his strong thumbs and get hoisted into the air.

At 60, he became a marathon runner, completing 11 races during the next 14 years, usually as one of the final finishers. Once in the D.C. Marathon, he gave his last-place "paper crown" to a young man with Down syndrome who finished ahead of him so the other man could take something home for his efforts.

Those were some of the fun ways he hewed to his youthful idealism. But Prouty, who had been a union lobbyist and government labor economist, also held strong views on very adult topics, such as racial and economic injustice.

Prouty died March 14 of complications from abdominal surgery, leaving behind children happy to have shared the playground with him, as well as adults who marveled at his drive to make the world right.

Writing in 1992 for his 50-year class reunion album at Dartmouth College, Prouty displayed a spirit of unfinished business: "We need not look far to see what humankind has done, within our own lifetimes, to this planet. If I were to start a second 50-year career at this moment, I would be inclined to choose activism on the environment as the next relevant step beyond labor activism."

He was first exposed to the labor movement while at Dartmouth, when his scholarship money ran low. After a short, dull stint as a Wall Street runner, he signed on as an oil tanker deckhand, spending his junior year at sea.

Later, while pursuing his master's degree in economics at Yale University, he worked on production lines in rubber factories. He felt such work gave him practical insight into how unions worked and what union members wanted.

Prouty held a succession of research and lobbying jobs for unions in Connecticut and Ohio before moving to the Washington area in 1966. He worked in similar jobs here before joining the Transportation Department in 1975. He retired in 1994 as a liaison between the office of the secretary and unions for airlines, railroads, trucking and mass transit.

Dick Walsh, former director of the Transportation Department's office of economics, marveled at Prouty's ability to get labor's views across to a department that tends to be friendlier toward business's interests. Walsh was even more impressed because Republicans controlled the White House for most of Prouty's tenure.

"It often looked like a lost cause, but Keith never thought of it as a lost cause," Walsh said.

Prouty's good relationship with union leaders helped him relay especially important information to his bosses, which made them look good, Walsh added.

Prouty had spent the last several decades involved in education and civil-rights issues. He was chairman of the Education Political Action Committee in Montgomery County, which helped elect a slate of liberal candidates, and was one of the few white men to hold ranking positions within the county and state NAACP, as well as the Black Ministers Conference of Montgomery County.

As an unpaid volunteer, he alerted the heads of those organizations to major bills in Annapolis that affected education, labor, health and public safety, and on which bills they needed to stake a position.

Last year alone, though he was ailing, he made 91 appearances before various committees.

Rep. Chris Van Hollen (D-Md.), a former Maryland state senator, said Prouty was a most unusual and ubiquitous presence, a man who dutifully floated among committee rooms without the Gucci varnish of pompous lobbyists.

"He was not there for any personal agenda or for special interest," Van Hollen said. "You have to always determine what people's agenda is, and with him you knew it was very simple. It wasn't about him. It was about issues that affected people who did not otherwise have a voice."

He said politicians regarded Prouty as "a highly respected voice of conscience."

Last December, Prouty postponed a hip-replacement operation and asked doctors for cortisone injections to alleviate the pain. That way, he did not have to miss the General Assembly's legislative session, which began Jan. 8.

He was hospitalized Jan. 12 for what seem be a recurrence of an ulcer and spent the last several months of his life in intensive care as complications arose. He remained on a respirator and unable to talk.

His wife, Muriel, and their four children updated him on their lives and, as they knew he would want, about legislation in Annapolis.

"I've been going through his briefcase," Muriel Prouty said, "and there's a list of all the bills he was going to get involved in."

Whether he was around a finish line or a picket line -- or lying around with a pooch --

Keith Prouty brought a youthful spirit to all the activities he was passionate about.