Four times in the past few weeks, the obituary pages have reported deaths of men for whom this reporter's professional respect was mingled with fellings of personal affection and gratitude.

William J. Baroody Sr., the former president and guiding spirit of the American Enterprise Institute; Albert B. (Ab) Hermann, a longtime official of the Republican National Committee; Donald G. Herzberg, the dean of graduate studies at Georgetown University; and former governor James B. Longley of Maine -- unique and distinctive individuals, with little in common. But they exemplified four qualities that give vitality to our society and our politics and that are diminished by their deaths.

Bill Baroody believed in the power of ideas. He came to Washington as an advocate of free enterprise in a capital dominated by New Deal thinking. While advising two generations of Republican presidential contenders, his main purpose was to build an intellectual center of conservative thinking that could challenge the prevailing orthodoxy.

The American Enterprise Institute is that center, and it expanded under his 25 years of leadership from a ragtag outfit to an organization whose scholarly activities, conferences and publications rival those of its more liberal neighbor, The Brookings Institution.

Because Bill Baroody believed in open political debate, AEI has also become a place where dissenters from today's fashionable conservatism are welcome -- and where the discussions are both civil and stimulating.

And Ab Hermann was a very different fellow -- a street-smart politican whose vocabulary always bore the stamp of his Milltown, N.J., upbringing and his eight years as a third baseman with the old Boston Braves. Ab Hermann believed in the Republican Party in the same simple, fundamental way that he believed in his Colgate University athletic teams and in the value of competitive sports.

For almost 30 years, he was the unchanging presence on the political staff of the Republican National Committee, taking an unending succession of chairmen through their initiation rites and showing them which skeletons occupied which closets and how to keep them still.

For dozens of reporters (including this one, when I was barely able to find my way from the Cafritz Building GOP Headquarters to Capitol Hill), Ab Hermann was also a guide. Without the least trace of disloyalty to his party, he would -- by the lift of an eyebrow or one of his fractured, Casey Stengel sentences -- steer you toward reality, or at least to the Republican version of that elusive prize.

Don Herzberg was every bit as partisan a Democrat, but what distinguished him was his faith in young people and his devotion to the nurturing of their political telents. He did not make it easy for anyone to discover that fact; for, despite his academic career, he affected the pose of a tough-talking pol -- someone who had no patience, for example, with the "reforms" of the Democratic convention and nominating process.

But his life work was teaching. Before coming to Georgetown, he had spent 17 years making the Eagleton Institute of Rutgers University one of the great graduate centers of politics in this country.

Don Herzberg had a particular affinity for practioners, and not just scholars. He found them in places that fashionable opinion scorned. Under his leadership, Eagleton developed a program for identifying and coaching the most promising young state legislators in seminars designed for their special needs -- and this at a time when the press and public did nothing but ridicule the legislatures as the sewers of politics.

The subsequent careers of those men and women are the best proof that Herzberg's faith was justified.

Jim Longley, the last of these four friends, was a man with enormous faith in himself. That is a trait of every successful politician, of course, but Longley possessed it to a degree I have rarely seen.

It made him a difficult, prickly person to deal with on many occasions. But that was a small price to pay for a relationship in which the intensity of one man's convictions forced an equally honest response from the other.

He had been a smashingly successful insurance salesman before he was drawn into politics by his work on a commission examining the operations of the Maine government. What he saw convinced him he could run Maine better than anyone else. When he decided that, he simply ran for governor as an independent, scorning to bend to the demands of the party nominating process.

He won in 1974 -- to everyone's surprise but his own -- and quit in 1978, as he had said he would, satisfied that he had proved his point.

I said at the outset that these men were strikingly different from each other. But it occurs to me that there were some common threads. Jim Longley's only campaign button read "Think about it," a slogan Bill Baroody would have liked.

The legacy of his independent governorship in Maine is a strengthened two-party system, with both Democrats and Republicans in that small state presenting the voters with an exceptional quality of young leadership -- something Ab Hermann and Don Herzberg would have loved.

They will be missed for what they were -- and what they did.