Investigative reporters are, by their nature, dogged, tenacious and deeply suspicious, crashing through official roadblocks as they chase the most elusive stories.

Some of them continue that quest long after their support evaporates, their evidence crumbles and even their employers abandon them.

Mary Mapes, the CBS producer fired over the journalistic fiasco involving President Bush's National Guard service, is the latest in a line of lonely crusaders, defending her work more than a year after it was widely discredited. Dan Rather may have apologized for the story, an independent panel may have denounced it and CBS News may have criticized her "disregard for journalistic standards," but Mapes argues in her new book that the critics are either politically motivated, cowardly or just plain wrong.

In challenging those who have questioned her work -- including The Washington Post and this reporter, who is cited in the book for a triple-bylined news story recounting the mess -- Mapes displays the relentless qualities that all good diggers share. But she also opens herself up to the charge that her obsession has clouded her judgment.

Mapes is right that the purported 30-year-old memos by Bush's long-dead squadron commander have not been proven to be forgeries, but is that the standard for broadcasting a serious charge? The documents have not been proven real, either, and endless debates about superscript and proportional spacing are not likely to change that.

In the same week that Mapes's "Truth and Duty" was published, Judith Miller was forced out of the New York Times after years of controversy. Miller, too, had lost the support of her news organization -- her executive editor, while praising her past contributions, had accused her of misleading the paper in the Valerie Plame leak investigation -- and her take-no-prisoners style had alienated many of her colleagues.

Unlike Mapes, Miller finally acknowledged, more than a year after the fact, that her stories on Iraq and weapons of mass destruction had been wrong. But she expressed no regrets about this, saying matter-of-factly that "if your sources are wrong, you are wrong." There was "lingering fury" toward her, Miller told CNN's Larry King, because some of her stories "had turned out to be based on faulty intelligence."

Not that Miller was a passive conduit. When the Army unit with which she was embedded in 2003 was ordered to pull back from its search for illegal weapons, Miller wrote military officials: "I intend to write about this decision in the NY Times to send a successful team back home just as progress on WMD is being made." The order was later rescinded.

Miller deserves credit for her willingness to go to jail rather than testify about her conversations with I. Lewis "Scooter" Libby. Yet she continues to defend her decision to leave jail 85 days later and testify, despite criticism that this undercut her original stance. She has accused editors at the paper of "unsubstantiated innuendo" and "ugly" and "inaccurate" criticism -- a turbulent end to a career in which she was part of a Pulitzer Prize-winning team.

April Oliver, a former CNN producer, also wound up at war with her ex-bosses. She sued the network in 1999 over its retraction of her story alleging that U.S. soldiers used lethal nerve gas in Laos during the Vietnam War. Oliver and a second producer were fired, and correspondent Peter Arnett reprimanded, when CNN and Time apologized for the "Operation Tailwind" story.

Just as Mapes has denounced the independent CBS inquiry co-chaired by former attorney general Richard Thornburgh, Oliver assailed CNN's outside investigation, headed by attorney Floyd Abrams, as a whitewash. One of Oliver's sources, retired Adm. Thomas Moorer, later denied the story. Oliver wound up suing another of her sources, retired Maj. Gen. John Singlaub, who in turn sued her and the news outlets. Oliver, who eventually settled her suit against CNN, told The Washington Post Magazine that the military had "gotten to" some of her sources.

Perhaps the saddest case involved Gary Webb, a San Jose Mercury News reporter who suggested in a 1996 series that the CIA knew a drug ring linked to the Nicaraguan contras had been selling crack in Los Angeles. When the "Dark Alliance" series caused an uproar, the Mercury News editor concluded after a review (and critical pieces in other major newspapers) that it "fell short" of the paper's standards. Webb, who called the findings "bizarre" and "nauseating," left the paper after being demoted. He committed suicide last year.

Not all investigative reporters stand by discredited stories. While researching a 1997 book on JFK, Seymour Hersh was taken in by Lawrence Cusack III, who was peddling what turned out to be fake Kennedy documents. But Hersh concluded he'd been had, deleted the material from "The Dark Side of Camelot" before publication and helped expose Cusack, who was convicted of fraud.

Mapes, however, did not lose faith in her story even after her key source, former National Guardsman Bill Burkett, admitted lying to her about where he obtained the disputed documents. Nor was she swayed by criticism from some of the document experts hired by CBS to vet the papers (one of whom, Emily Will, recently set up a Web site to denounce Mapes's book).

Instead, Mapes continues to argue that the "60 Minutes II" segment was "well researched and well documented" and that CBS and its corporate parent, Viacom, caved to pressure by abandoning her and the story.

"What CBS News did was choose to handle this in the most divisive way possible by launching an investigation that forced people to turn against each other, by questioning its employees, and by believing conservative bloggers instead of people who worked for them for decades," Mapes told CNN.

Actually, what CBS did was try to salvage its reputation by asking outsiders to evaluate a story that its news division could no longer defend.

Without the determination of investigative journalists to ignore outside pressure while turning over every possible rock, some important secrets would never be uncovered. But sometimes the reporters never hit pay dirt and just dig themselves into a deeper hole.

Footnote: The controversy surrounding Bob Woodward involves not an inaccurate story but the holding back of information. Woodward, the Washington Post sleuth who apologized last week for not telling his bosses that a senior administration official had discussed Plame with him in 2003, has drawn criticism from some colleagues over his unique role in which he basically writes books while remaining on the Post payroll. He gave his detractors ammunition by commenting on the case while keeping quiet about his involvement. Those who say that Woodward's extraordinary access to top administration officials has made him too much of an insider have a point, but they forget that his books invariably produce news, often about conflicts among those officials.

Plagiarism Watch

Ken Parish Perkins, television critic for the Fort Worth Star Telegram, resigned last week after being confronted with several instances of apparent plagiarism.

After a caller noted that Perkins had used a paragraph as it appeared verbatim in Entertainment Weekly, editors found several pieces in which he had lifted long phrases or sentences without attribution. Perkins was such a hard worker that "it's so hard for us to understand why this happened," Editor Jim Witt was quoted as saying.

Meanwhile, the Bakersfield Californian found that more than a third of the 96 stories written by Nada Behziz contained "plagiarized material, misattributed quotes and information, factual errors or people whose existence could not be verified -- including seven physicians and a UCLA professor." Behziz, who was fired last month, told the paper: "This is a witch hunt. Too bad your news organization is not this vigilant in pursuing true wrongdoers."

And Furthermore . . .

After that verbal brawl in the House over Iraq, New York Times | http://nytimes.com/2005/11/20/politics/20cong.html?hp&ex=1132462800&en=57b699284e6b3bba&ei=5094&partner=homepage says the war could be the '06 issue:

"The ferocity of the fight in the House over a measure to withdraw American troops from Iraq shows that the war may command the high ground in the coming electoral contest, and that the course of events in Iraq - whether a new government takes hold, whether the violence continues, whether American troops are still committed in large numbers and still being killed by the scores each month - will be of prime political consequence here."

Conservatives have been pooh-poohing the John Murtha news conference by chiding the press, saying the Pennsylvania congressman has long been a critic of the war. But this is the first time he has called for an immediate withdrawal.

But Ron Brownstein notes in the LAT | http://www.latimes.com/news/politics/la-na-assess20nov20,1,5347669.story?coll=la-headlines-politics: "While the week's events demonstrated rising Democratic hostility to the war, they also underscored the party's continuing divisions over what alternative to offer -- and whether to present a specific alternative at all. Though some insiders believe a majority of House Democrats might ultimately endorse Murtha's proposal to begin an immediate withdrawal from Iraq, only 13 so far have co-sponsored the resolution embodying it."

The Philly Inquirer | http://www.philly.com/mld/inquirer/13212009.htm finds no anti-Murtha backlash at home: "Mostly, people in Murtha's blue-collar, coal- and steel-country district in southwestern Pennsylvania signaled weariness of the war. They endorse the man who has represented them since he became the first Vietnam War veteran elected to Congress in 1974."

Newsweek's Howard Fineman | http://www.msnbc.msn.com/id/10118733/site/newsweek/ calls Murtha a "one-man tipping point" and says "the political center of gravity suddenly shifted to another question: how we get out."

Washington Monthly's Kevin Drum | http://www.washingtonmonthly.com/archives/individual/2005_11/007583.php sees a paradigm shift as well:

"Over at The Corner, even Rod Dreher | http://corner.nationalreview.com/05_11_13_corner-archive.asp#082858 was impressed:

"As I listened to it, I could feel the ground shift. Murtha, as you know, is not a Pelosi-style Chardonnay Democrat; he's a crusty retired career Marine who reminds me of the kinds of beer-slugging Democrats we used to have before the cultural left took over the party . . . From where I sit, conservatives would be fools not to take this man seriously.

"My prediction: we've already started to see this, but I think Republicans are about to crumble. Pressure is going to mount on the White House to use the December elections as an excuse to declare victory and go home, fueled by equal parts disgust over Dick Cheney's lobbying for the right to torture; unease even among Republicans that the president wasn't honest during the marketing of the war; lack of progress on the ground in Iraq; Congress reasserting its independence of the executive; a genuine belief that the American presence has become counterproductive; and raw electoral fear, what with midterm elections looming in less than a year.

"I also think the Rove/Cheney/Bush counterattack is going to backfire. Congressional Republicans are looking for cover right now, and I don't think they believe that a ferocious partisan attack from the White House is what they need right now. The public is looking for answers, not administration attack dogs on the evening news every day, but this particular White House doesn't know any other way. It's going to cost them."

The new Weekly Standard responds to Murtha in an editorial:

"Rep. Jack Murtha has had a distinguished congressional career. But his outburst last Thursday was breathtakingly irresponsible. Nowhere in his angry and emotional call for the immediate withdrawal of U.S. troops from Iraq did the Pennsylvania Democrat bother to ask, much less answer, the most serious questions his proposal raises. What would be the likely outcome in Iraq if the United States pulled out? Does Murtha actually believe the Iraqi people could fight the al Qaeda terrorists and Saddam Hussein loyalists by themselves once American forces left? He does not say. In fact, he knows perfectly well that the Iraqi people are not yet capable of defending themselves against the monsters in their midst and that, therefore, a U.S. withdrawal would likely lead to carnage on a scale that would dwarf what is now occurring in Iraq."

Matthew Yglesias | http://yglesias.tpmcafe.com/ says Murtha better get his flak jacket:

"Another solid E.J. Dionne column is marred by one unfortunate claim: 'It will be difficult for Bush's acolytes to cast Murtha, who has regularly stood up for the military policies of Republican presidents during his 31 years in Congress, as some kind of extreme partisan or hippie protester.' Consider highly-decorated war hero John Kerry. Or victorious General Wesley Clark. Veteran ambassador Joe Wilson armed with a letter of commendation from Bush's father and dispatched by the Bush administration itself to investigate an intelligence matter. Or Larry Wilkerson and Richard Haas from Bush's State Department. Paul O'Neil and John DiIulio. Richard Clarke. Brent Scowcroft. Zbigniew Brzezinski. Paul Hackett. One could go on.

"Maybe it was 'difficult' to paint these people as extreme partisans, but it wasn't so difficult that it couldn't be done. The idea that there's some person out there whose biography will somehow make him immune to Republican attacks is a dangerous myth. A good biography helps in politics, better to have one than not to have one."

Along those lines, here's Scott McClellan's response to Murtha: "It is baffling that he is endorsing the policy positions of Michael Moore and the extreme liberal wing of the Democratic Party." And Jean Schmidt, the newest member of Congress, said during the uproar over the GOP's stunt of a pullout resolution that her message for Murtha is "cowards cut and run."

That drew this blast from Andrew Sullivan | http://www.andrewsullivan.com/index.php?dish_inc=archives/2005_11_13_dish_archive.html#113235774456563711:

"For the record: Murtha served 37 years in the Marines, and has Purple Hearts to his name. He visits wounded soldiers at Walter Reed every week. Three years ago, he won the Semper Fidelis Award of the Marine Corps Foundation, the highest honor the Marines can confer. Every time you think these Republicans can sink no lower, even after their vile smears against Kerry's service last year, they keep going. They make me sick to my stomach."

Rich Lowry | http://nationalreview.com/lowry/lowry200511180820.asp sees a silver lining in all the storm clouds for the GOP:

"Republicans are losing the air game. They are associated with an unpopular war. They are beset by scandal. A Republican president is scraping along at new lows of public approval seemingly every week. And they appear to have run out of ideas, at least ones that they can govern on. But the ground game is another matter.

"After ten years in the majority, House Republicans have become master electoral mechanics; they know the advantages of incumbency the way your plumber knows your sink. The chairman of the House Republican Campaign Committee, Rep. Tom Reynolds of New York, calls it fundamental "block and tackle" politics. It is an unglamorous, uninspiring formula, but one that makes it very likely that even after suffering a year that could hardly be more dreadful, the House Republican majority will live to fight another day.

"The vision that Democrats have dancing through their heads is the debacle that swept them from power in 1994, only in reverse. Democratic Congressional Campaign Committee Chairman Rahm Emanuel compared the Republican inability to muster a majority on a key budget bill on Nov. 10 to the Democratic loss on a routine procedural vote on a crime bill in the summer of 1994. That crime-bill defeat symbolized a Democratic breakdown that brought the end of their majority months later.

"But such a shift next year -- Democrats need a net gain of 15 seats -- would require something that has been increasingly wrung from our congressional elections: competition. Sophisticated redistricting makes it possible to finely craft district lines to suit the interests of their current occupants. It used to be that redistricting would be done on gasoline-station road maps. Now anyone can buy software for $200 or so that makes protecting incumbents an exact science."

Of course, next year's elections are still a long way off.