DARREN BOOTH

Senator Joseph McCarthy claimed his place in the history books by telling a crowd in Wheeling, W.Va., that the State Department was full of Communists. “We are not dealing with spies who get 30 pieces of silver to steal the blueprint of a new weapon,” he said. “We are dealing with a far more sinister type of activity because it permits the enemy to guide and shape our policy.” The claim was baseless, scurrilous — and plagiarized. The same words, practically verbatim, had been spoken on the floor of the House of Representatives two weeks earlier, by Representative Richard M. Nixon of California.

Senator McCarthy’s wholesale borrowing was discovered only years later. Had reporters noticed it sooner, he might have run into a different kind of trouble than he did, for the press loves a plagiarism quarrel. Consider the well-aired sins of numerous writers in recent years — and last week’s back-and-forth over Senator Barack Obama’s uncredited use of the words of others.

Last weekend it was reported that Mr. Obama used on the presidential campaign trail a rhetorical set-piece first spoken by Gov. Deval Patrick of Massachusetts, a friend and co-chairman of his campaign. The sequence contained famous political lines followed by the refrain “Just words” — a gibe meant to rebut the taunt of his rival, Senator Hillary Rodham Clinton, that he offers voters only speeches, not deeds. Mr. Obama acknowledged that the failure to cite Mr. Patrick was an error, if an unimportant one. In Thursday’s debate, Mr. Obama said he thought it was “silly” that this was even under discussion. Mrs. Clinton pressed the case, saying, “If your candidacy is going to be about words, then they should be your own words.”

Mr. Obama is unusual among politicians for having written a memoir praised for its literary skill and for being the author of at least some of his own finely wrought speeches. That reputation is partly why the suggestion of plagiarism was startling to some. Hendrik Hertzberg, who was a speechwriter for Jimmy Carter, wrote on his blog at newyorker.com that Mr. Obama’s was “not a mortal sin,” but rather a “damaging mistake ... given that Obama’s eloquence and ‘authenticity’ are so central to his appeal.”

When professional writers borrow words without attribution, they’re frequently censured, sometimes fiercely. It’s natural, however, that when politicians do something similar — and particularly when the words are spoken — they are forgiven.

As Thomas Mallon, author of “Stolen Words,” a book about plagiarism, points out, “Political language is unusually fluid.” Politicians routinely borrow from one another, especially during campaigns, when they make use of any themes or mantras that seem to work. What Democratic candidate hasn’t vowed to “fight for working families”?

Historically, most politicians who fail to credit sources emerge unscathed. In 1970, Vice President Spiro T. Agnew gave a speech that lifted chunks of prose from two N.A.A.C.P. policy experts. One of the experts said he was “delighted,” since it meant that Mr. Agnew was adopting his liberal policies. In 1987, it came out that the Democratic House speaker, Jim Wright, had given a speech in Berlin that presaged President Reagan’s “tear down that wall” remarks two months later. Though reportedly miffed, Mr. Wright let the matter go, saying, “I’m not going to sue him for plagiarism.”

There is “a different standard for writing and for speaking,” said Deborah Tannen, a linguistics professor at Georgetown University. “Spoken words are more in the public domain.”

But even cases of written appropriation in politics tend to cause little fuss. In 2004, the conservative newspaper The New York Sun reported on writings by the Democratic presidential nominee, John F. Kerry, that closely tracked other people’s published articles. The accusations went all but unnoticed. In the 2006 Virginia Senate race, the Republican George Allen accused his Democratic challenger, James Webb, of putting a historian’s published words into his novel without giving credit. Mr. Webb won the race.

The public tends to dismiss these episodes partly because the use of speechwriters has changed the standards for originality in politics. Audiences don’t kid themselves that politicians invent the words they speak. Theodore C. Sorensen, the speechwriter for John F. Kennedy who is aligned with Mr. Obama’s campaign, said that precisely because speechwriters are ubiquitous, they’re seen as extensions of the politician. “It’s the speaker who puts his name on it, who takes responsibility for it,” he said. “If the speech fails, he’ll reap the consequences. If it’s a success, he should get the credit, even if he didn’t pen the words.”

The tacitly accepted distinction between reciting a hired hand’s slogans and usurping paragraphs from another individual led to the end of the 1988 presidential bid of Senator Joseph R. Biden Jr. of Delaware. Mr. Biden, then 44, appropriated the content of a speech from the British politician Neil Kinnock — including biographical details, like being the first in his family to attend college, that didn’t apply to Mr. Biden. More uncredited borrowings surfaced, including phrases from Robert F. Kennedy and Hubert Humphrey. Soon, the news that Mr. Biden had committed plagiarism in law school led him to end his campaign.

Not even the Clinton camp is suggesting that Mr. Obama’s infraction matches Mr. Biden’s. “The one parallel,” says Mr. Mallon, who like most others interviewed for this article considers the Obama incident to be trivial, “is that Biden was seen as the best orator in the field in 1988. It went to the heart of his candidacy.”

Judge Richard A. Posner of the United States Court of Appeals for the Seventh Circuit, author of “The Little Book of Plagiarism,” suggests that Mr. Biden’s offense had a special element of falsity. “What did Biden in was he seemed to be appropriating someone else’s life. That was creepy,” he said.

Another key difference, as Mr. Obama has stressed, was that Mr. Patrick “gave me the line and suggested I use it.”

But, the Obama case aside, having the blessing of the source doesn’t necessarily render uncredited use benign. Those potentially hurt include not just the originator of the words but the audience. “It seems to me the focus should be on the audience — is the audience hurt, is the audience deceived?” Judge Posner said.

And the competition may be hurt too. Just as a student who plagiarizes gains an unfair advantage over others, Judge Posner said, a candidate’s rivals may suffer in comparison to a plagiarist.

It may be that the Obama incident has sparked debate because his orations have struck many as a welcome exception to the poverty of political speech in general. “Political language today is less idiosyncratic, less original, certainly less literary and less inspiring,” Mr. Mallon said. “These candidates have got to treat words as cheap because they do so much to cheapen language by their endless droning and repetition.”

David Callahan, author of “The Cheating Culture: Why More Americans Are Doing Wrong to Get Ahead,” said, “It’s very common for politicians to issue talking points that are then deliberately repeated almost verbatim by tons of people. These people are not in the originality business. The point is to create an echo chamber.”

Mr. Sorensen suggested that television was partly to blame for the decline. “TV is in the living room, it’s in the bedroom, it encourages casual talk. Casual talk is fine, but there’s something to be said for the elevated and inspiring level of rhetoric that John F. Kennedy provided and that,” he added, in support of his current candidate, “Barack Obama is providing today.” David Greenberg teaches history and media studies at Rutgers University and is the author of “Nixon’s Shadow” and “Calvin Coolidge.”

Copyright 2008 The New York Times Company. Reprinted from The New York Times, Week in Review, of Sunday, February 24, 2008.