WASHINGTON // The favourite to win the Republican nomination to run for president, Mitt Romney is suddenly looking a bit vulnerable ahead of today's primary in South Carolina.
In spite of a comfortable lead in the conservative southern state only last week, Mr Romney apparently has lost some ground to his closest rival, Newt Gingrich, the former leader of the House of Representatives.
His problem? If campaign advertisements are to be believed, Mr Romney, the former governor of Massachusetts, speaks French and so does John Kerry, a senior Democrat senator, also from Massachusetts.
That was the conclusion of an ad sponsored by Mr Gingrich's campaign and now flooding South Carolina. Entitled The French Connection, the ad seeks to paint Mr Romney as a closet Democrat who "would say anything … anything" to appear conservative.
The French Connection is just one of a cascade of so-called attack ads - advertisements that seek to discredit another candidate's record or character - that have featured heavily in the Republican race to run against Barack Obama for the US presidency in November.
Some come directly from the individual campaigns. Some, usually the more extreme, come from super-Pacs - ostensibly unaffiliated political action committees that can spend unlimited sums promoting any candidate or issue they want.
Candidates profess to hate them. In Iowa, Mr Gingrich decried as "unworthy of America" an ad that called into question both his political record and personal life and characterised him as "unable to transform, or even govern, himself".
The ad was so harsh that Mr Romney distanced himself from it, even though it had been paid for by a super-Pac that supports his candidacy.
Millions are spent on attack ads even though there is no evidence they have much effect, according to Lynn Vavreck, an associate professor of political science at the University of California, Los Angeles. Ms Vavreck has just concluded a project studying political advertisements that finds that their effect is minimal.
"To the extent that these attack ads are working at all, the effect they're having is gone within two to three days of being aired."
However, people tend to learn more about a candidate's position on issues from attack ads than they do from promotional advertising, Ms Vavreck said.
"From the perspective of, are they good for democracy: if you want an electorate that has more information, then, yes, these attack ads are providing that."
Negative campaigning has a long history in America. In 1828, supporters of the incumbent John Quincy Adams tried to paint Andrew Jackson as immoral because he had mistakenly married before his intended spouse had finalised her divorce. Jackson, in turn, accused Adams of using public money for gambling equipment - later revealed to be a chessboard and a pool table. Jackson won the election easily.
Technology ushered in new tools for delivering attack messages. In 1964, an ad for Lyndon B Johnson cut from footage of a small girl picking petals off a daisy to a nuclear explosion to suggest that voting for Barry Goldwater could lead to nuclear war.
In "the aggregate", said Jeffrey Weiss, a Washington-based political consultant and veteran of several Republican campaigns, history suggests negative campaigning works. And attack ads work, he said, because they "define the other guy".
"Some people go overboard and it looks like genuine mudslinging," Mr Weiss said. "But for the most part, I think they define the other guy. And unless he answers back and figures it out, they take their toll."
At the moment, Mr Romney is having to provide a lot of answers. As the front-runner, the multimillionaire businessman who made his fortune with Bain Capital, a private investment firm, is having to defend his claim that being successful in the private sector uniquely qualifies him to lead the country.
Winning the Future, a super-Pac supporting Mr Gingrich, recently launched an ad characterising Mr Romney as a "corporate raider" who enriched himself on the backs of American workers.
The ad, King of Bain, was in part funded with a US$5 million (Dh18.4m) donation from Sheldon Adelson, a billionaire Las Vegas casino magnate, pro-Israel lobbyist and vocal supporter of the policies of Benjamin Netanyahu and Israel's Likud Party.
Mr Gingrich has promised to make it a priority to move the US Embassy in Israel from Tel Aviv to Jerusalem, and the recent injection of Mr Adelson's cash to Winning the Future appears to have given Mr Gingrich new impetus.
Airtime is costly and if negative ads have a short shelf life, as Ms Vavreck's studies suggest, they must be aired frequently and "you have to run them to the very end".
King of Bain is "potent", said Mr Weiss. By portraying Mr Romney as among the "Gordon Geckos of this world" - referring to the Michael Douglas character in the movie Wall Street - the ad "taints" the former venture capitalist, Mr Weiss said.
The bitter Republican infighting has caused some in the party to worry that Mr Obama will benefit from it. But Mr Weiss said the eventual candidate will have to learn to deal with attacks sooner or later.
"If they don't do it now, they will certainly have to do it in six to eight months."