Dead now for 50 years, Senator McCarthy and the movement named for him remain a favorite boogeyman for many liberals. In a history lesson promoted repeatedly since the 1950s, the late senator and his crusade are presented as follows:

Eager for a re-election issue in 1950, McCarthy hops on the anti communist bandwagon by offering lists of communists in government employ. When questioned about specific charges, McCarthy instead attacks fresh victims. Along the way he attracts unsavory fascist sympathizers, angry since the New Deal. The political climate, already hysterical in the early nuclear era, grows worse because of McCarthy’s crusade. Books are burned; distinctions between New Dealers and Stalinists become even more blurred in the public consciousness. Out on a limb, it only takes a canny lawyer named Joseph Welch with a flair for the put-down (“Have you no sense of decency, sir?”) to break it. Adding army generals to his list of suspected communists, McCarthy is checkmated by the Army and plummets in the polls. Disgraced, censured, McCarthy drinks away three more years and dies.

There are elements of truth in this account, but ultimately McCarthy was a more complex character, and his crusade a more complicated one, than ideologues of either stripe often admit. Against the vivid backdrop of the conventional account, though, M. Stanton Evans, a writer for Human Events magazine, will convince few liberals across the aisle that McCarthy was correct in his attempts to prove security breaches on the watch of presidents Roosevelt and Truman with his thorough new study, “Blacklisted by History: The Untold Story of Senator Joe McCarthy and His Fight Against America’s Enemies” (Random House, 644 pages, $29.95).

With a painstaking reliance on documentation (decrypted Soviet cables, secret Congressional testimony, declassified FBI files), Mr. Evans presents the case for McCarthy that Whittaker Chambers once said the senator was “unwilling or unable to make for himself.” Many of those investigated by McCarthy were grouped in an earlier list of subversives by the Roosevelt administration in the early 1940s, and some have since been confirmed as spies by the Venona telegrams, a series of intercepted transmissions from and to Moscow by their American agents during World War II, which were released for public consumption in 1996.

With his determination to source everything, Mr. Evans’s presentation is not particularly page-turning. But the reality that Mr. Evans presents is disturbing. In the 1930s and ’40s, despite warnings from the FBI, presidents laughed away charges that their employees were Soviet spies. Confronted with evidence about a State Department official, Alger Hiss, FDR merely waved his hand and said, “Drop it. There’s nothing there.” Government employees carting away papers to Soviet couriers in the dead of night were advanced up the career ladder: Hiss was placed in charge of security at wartime conferences; Gustav Duran, a part of the Loyalist secret police that was hunting George Orwell in Spain, was moved into the Office of Strategic Services; Cedric Belfrage, a Soviet agent, was promoted to security coordinator between wartime British intelligence and America. Despite warnings from the FBI that J. Robert Oppenheimer was still a secret party member, General Leslie Groves put him in charge of the secret Manhattan Project.

The only entities even attempting to halt these penetrations and leaks were the House Un-American Activities Committee, that rogue’s gallery of anti-Semites and future perjurers, and McCarthy, already boozy by the late ’40s, unorganized, and hungry for publicity. Only they seemed to be blind to the threat. Prosecutors are fond of countering character attacks on their witnesses by asking rhetorically, “Why can’t a criminal have good eyesight?” Whatever McCarthy’s peccadilloes — and they are more numerous than Mr. Evans acknowledges — his vision was at least clearer on this question than that of the liberal establishment.

But Mr. Evans’s focus is so fixated on validating McCarthy’s crusade through documentation that he avoids asking pressing and disturbing questions about the senator himself. If he wasn’t trying to heighten the hysteria, why did McCarthy resort to the sensational, such as calling Far East expert Owen Lattimore “the top Soviet espionage agent in the US,” which he clearly wasn’t, instead of a fervent fellow traveler of Stalin, which he demonstrably was. Or accuse Gen. George Marshall, a man whose only crime was stupidity about Mao, of being a Soviet spy? Why, if he was truly motivated only by stopping the Soviet penetration of the American government and not publicity, did McCarthy go after mystery writer Dashiell Hammett, whose party activities consisted of cranking out agitprop and signing his name to petitions? Why did he allow Roy Cohn and G. David Schine to use taxpayer money for posh hotels overseas in their “quest” for detecting communist books in American government libraries? The probable answers point to hunger for publicity or recklessness, or alcoholism — possibly all of the above — and these are not the characteristics of one totally committed to a cause. These personal flaws don’t lessen the culpability of McCarthy’s targets, of course, but by avoiding McCarthy’s character defects, Mr. Evans opens himself up to those who will charge him with being the most fervent kind of embattled partisan, one who cannot allow any criticism into an argument, out of fear the whole edifice will crack.

Mr. Capshaw has written for the Weekly Standard, Partisan Review, FrontPage Magazine, and National Review. He lives in Richmond, Va., and is working on a biography of Alger Hiss.