By Stephen Sackur
Presenter, HARDtalk, BBC World News
Over the past few weeks of the US presidential election campaign, the tone has turned increasingly negative, especially from the Republican side.
BBC News has been talking to two key Republican advisers about whether the personal attacks on Senator Obama can be justified.
Across America, ghosts, ghouls and snaggle-toothed jack o'lanterns peer out from a million suburban stoops; it is just two weeks until Halloween.
This may be the year for the politicians to save the scare tactics for Halloween
But this fall. a genuinely frightening spectre is said to be lurking in the bushes, ready to pounce on the good people of Middle America.
He is tall and slim but his past is dark. He 'pals' with a terrorist intent on blowing up American values.
He was raised in a strange land amongst Muslims. His religious mentor in more recent times is a preacher of hate.
His name alone is enough to strike fear into many a God-fearing soul. Whisper it quietly: Barack Hussein Obama is coming to get you.
Over the top? You bet, but then that is the tone adopted by some of the die-hards in the Republican campaign for the White House.
Do you know whether radical Islam was part of Barack Obama's background?
Gary Bauer, president, American Values
Early this month they looked at the polls showing a significant and growing Obama lead. They saw the economy in a tailspin and they felt the anger of a nation disgusted by Wall Street greed. And they reached a conclusion: it was time to go negative.
Bill Kristol, editor of the Weekly Standard and prolific advocate of the Conservative cause, put it this way:
"The McCain campaign has to convince 51% of voters they can't trust Barack Obama to be our next president".
In an interview with BBC News HARDtalk programme, Mr Kristol described how he had discussed the campaign with Republican vice-presidential candidate Sarah Palin.
She expressed her determination to tell Americans "who the real Barack Obama is."
Within days Ms Palin, the self-styled pitbull with lipstick, was accusing Obama of 'palling around with terrorists' - a reference to his relationship in his Chicago past with William Ayers, a one-time leader of the Weather Underground, which launched a haphazard and short-lived campaign of violence against the US Government in the 1960s.
The charge was repeated by Senator McCain in his final debate on Wednesday.
Mr Ayers has for many years been a university academic and community activist. He was named Chicago's 'Citizen of the Year' in 1997.
Mr Kristol defended the William Ayers line of attack on Senator Obama as fair game.
He, like many other Republicans, knows that negative campaigning has worked in the past.
Hussein and Sidney
But how far can the Republicans go?
At one recent McCain/Palin rally the candidates were introduced to the stage by a local activist, Bill Platt, who warmed the crowd up with these words:
"Think about how you'll feel on November 5 if you wake up in the morning and see the news, that Barack Obama -- Barack Hussein Obama -- is the president-elect of the United States. "
Although his father and step-father were Muslim, Mr Obama is a Christian
He went on: "The number one most liberal senator in the United States of America was, you guessed it, the ambassador of change, Barack Hussein Obama'"
Needless to say, Mr Platt did not introduce John McCain as John Sidney McCain, and it does not take an expert in semiotics to spot the key word in Mr Platt's peroration.
Obama's middle name, Hussein (taken from his Kenyan father), is for some on the social conservative right a signifier of his suspect status as an alien, a man with connections to a (frightening) Muslim world.
Christian conservative viewpoint
Gary Bauer is worried about Muslim influence on Mr Obama
I asked Gary Bauer, president of the Christian Conservative movement American Values, and an influential figure amongst the Republican base, whether this use of Obama's middle name made him uncomfortable.
His answer was revealing:
"Each person can make their own judgement about whether at a time that we live in when radical Islam has declared war on your country and my country, whether this is something that people want to weigh or not.
"Do you know whether radical Islam was part of Barack Obama's background? He went to a religious school in Indonesia. Nobody's been able to find out how things were run in that school.
"The people that were in the school at the time say it was a typical religious Muslim school, and they were being taught the things that we've seen being taught in many Muslim schools around the world that are troubling".
In the light of Mr Bauer's response, I was not surprised to hear that a lady in her seventies stood up at a McCain rally last week and referred to Obama as an 'Arab'.
McCain himself immediately contradicted her and described Obama as a 'decent family man' with whom he happened to disagree.
John McCain does not use 'Hussein', but he did choose Sarah Palin
It was an awkward moment which Senator McCain handled with dignity, but it points to a growing problem within his campaign.
The truth is the Republican candidate does not seem to have the heart for the deeply negative and personal campaign some of his own advisers want to run.
He has publically disavowed the use of Obama's middle name, but some of his supporters keep doing it.
He has refused to run negative advertisements about Obama's ties to the radical black pastor Jeremiah Wright even though conservatives are begging him to bring it back up.
With fewer than three weeks left until election day and Obama's poll lead widening, McCain may yet go negative with both barrels.
But Americans are preoccupied with economic worries. They want a President who can safeguard their jobs and their savings; a man who knows how to restore American strength not tear down the opposition.
This may be the year for the politicians to save the scare tactics for Halloween.
HARDtalk with Stephen Sackur is broadcast on BBC World News at 0330, 0830, 1430, 2030, and 2230. The interview with Gary Bauer will be broadcast on Thursday 16 October 2008.