By Richard Allen Greene BBC News Online

Scandal made it impossible for Nixon to remain in office

On 9 August 1974 Richard Nixon did something no US president before or since has ever done: He resigned.

His ignominious departure from the White House followed a break-in at the Watergate hotel headquarters of the Democratic National Committee.

The burglars were caught rifling through confidential papers and bugging the office of Nixon's political opponents - and they were linked to the president following investigation by Washington Post reporters Bob Woodward and Carl Bernstein.

The received wisdom has it that Watergate permanently changed American political culture, knocking the chief executive off his pedestal and emboldening the press.

But Stephen Hess, a presidential expert at the Brookings Institution in Washington, is not entirely convinced.

"For a relatively short period, that's correct," he told BBC News Online.

Ford moved to put the scandal in the past by pardoning Nixon

The humiliation of Nixon "created - for a while - an exuberant Congress and press that felt itself justified in terms of its investigative powers", he said.

"But over time the balance righted itself."

He credited Nixon's successor, Gerald Ford, with restoring respect for the presidency via his civility and decency.

He said Mr Ford was right to pardon Nixon so the country could put Watergate behind it.

And while Watergate created the precedent for the impeachment of Bill Clinton a generation later, the Clinton impeachment made it more difficult for Congress to impeach a future president.

"So it cycles again," Mr Hess said.

Long-term decline

John Samples of the Cato Institute said Watergate had indeed shaken Americans' confidence in their government - but that it was part of a much larger trend.

"Watergate was not the period when public trust in government was lowest or the year when the largest number of people thought officials were crooked," he said.

I would say only that if some of my judgments were wrong, and some were wrong, they were made in what I believed at the time to be the best interest of the nation Richard Nixon, announcing his intent to resign, 8 August 1974

Only 35% of people said they thought the government could be trusted "most of the time or just about always" in 1974 - but confidence had begun falling 10 years earlier.

"It started dropping in 1964 and continued until 1980. Watergate had a strong effect, but it was part of a story that had been going on for a decade before," he said.

It was 20 years after Watergate, in 1994, that trust reached its lowest level - 20% - and began climbing again, he added.

But other indicators showed Americans turning off politics around the time of Watergate, he pointed out.

The percentage of eligible voters casting ballots dropped sharply from 1968 to 1973, for example.

And he said Watergate had produced a "cultural shift for elites involved in politics".

"Before Watergate the president was a demi-god. People coming out and questioning the president's truthfulness in public was not something you did in 1965."

"Watergate destroyed that," he said, adding that the Vietnam war also played a role.

'Enormous impact'

Joseph Califano, a long-time Democratic party insider and lawyer who represented the Washington Post during the affair, agreed that the scandal had changed perceptions.

"Watergate had an enormous impact on the way statements by public officials were greeted by the press," he told BBC News Online.

He cited the media response to President George W Bush's recent terror warning as an example.

Press inquiries helped reveal that the alert was based on information several years old.

"That kind of scepticism would have been unthinkable before Watergate," he said.