Accusations about lobbyist are a smear, says McCain

John McCain, the near-certain Republican nominee, has flatly denied suggestions of impropriety, either romantic or professional, in his dealings with a female lobbyist and her clients eight years ago – a charge that if substantiated would strike at his most precious political asset, his reputation for integrity and for taking on special interests.

What McCain aides describe as "a smear" was set out in a long article in The New York Times, detailing his links with Vicki Iseman, a 40-year-old telecommunications lobbyist, as the Arizona senator was embarking on his first White House run in 2000.

With his wife, Cindy, at his side, Mr McCain declared himself "very disappointed in the article, it's not true". He considered Ms Iseman as a friend, he told a press conference called to address the issue. "At no time have I ever done anything that would betray the public trust or made a decision... which would favour anyone or any organisation."

Mrs McCain too said she was "very, very disappointed" by the reports, insisting that her husband – a decorated military hero and former prisoner of war in Vietnam – would never do anything to let down "his family or the people of America". A statement from Ms Iseman's lobbying firm yesterday described the article as "character assassination".

The most sensational aspect of the story is that various McCain campaign aides in 2000 were allegedly so concerned about his links with Ms Iseman, a constant visitor to his offices, that they confronted them both and warned her to stay away – especially after it emerged the senator had written letters to government regulators on behalf of her clients.

Yesterday Mr McCain claimed that his staffers had never raised the matter with him at the time. But Bill Keller, the editor of The New York Times, stood by the story, which had been "a long time in the works". Answering accusations that its appearance might have been timed to inflict maximum damage to the candidate, Mr Keller stated: "We publish when we are ready. On the substance, the story speaks for itself."

Although the events in question date back almost a decade, and no specific impropriety is alleged, the report has the potential to damage Mr McCain, by making him appear hypocritical, and by turning attention back to the murkiest chapter of his 25 years in elective politics.

In 1991 he was censured for intervening to protect the chairman of a failed savings and loan bank. The McCain narrative is that he was so chastened and shamed by the experience that he became an unremitting foe of corruption. In 2002, he co-authored a campaign finance reform bill clamping down on "soft money" channelled by special interests to political candidates, and later led the congressional investigation that helped bring down the tainted lobbyist Jack Abramoff.

Though the New York Times investigation unearthed no specific wrongdoing, it shows how Mr McCain took campaign contributions from companies whose business came up before the Senate committee which he chaired, and availed himself of standard perks such as the use of corporate jets provided by those companies.

Meanwhile, Mr Obama inched further ahead in the race for the Democratic nomination by winning the global Democrats Abroad primary, in which seven delegates to the Denver convention were at stake. It was his 11th straight victory over Hillary Clinton, with whom he was holding a televised debate in Austin, Texas, last night.

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