By the BBC's Gordon Corera

South Carolina has always been known for its tough politics.

After some relatively decorous debates early on in the primary campaign, there were high hopes - and some promises - that the candidates would not descend to mudslinging.

Now though the gloves have come off.

Rattled by John McCain's victory in the New Hampshire poll the Bush campaign has been throwing everything it has at the Arizona senator in a bid to halt his momentum.

At first both sides engaged in attacks. One McCain ad even went so far as comparing Bush to Clinton - a real insult in a state that has little affection for the President.

The ad claimed that by breaking his pledge not to attack his opponents, Bush showed that, like the President, he can't be trusted.

"Do we really want another politician in the White House America can't trust?" the ad asked.

Scoring points

But perhaps the most important event in the state came at a McCain rally in Spartanburg when a woman told the crowd that her teenage son had received a telephone call which described McCain as a "cheat and a liar and a fraud."

The startling outburst brought to light the controversial tactic of known as "push-polling".

Push polls involve voters being called up by a survey organisation employed by one of the candidate's campaigns and given information that may discourage them from voting from a candidate.

A typical call begins innocently as the voter is asked the kind of questions that a normal, independent survey would follow - such as whether someone is planning on voting or not.

If they say they are voting for McCain, then the tone changes.

The voter is asked whether they knew, for instance, that John McCain had been reprimanded by the Senate ethics committee, or that the Senator travels on the private jets of corporations that his committee oversees.

Negative info

After spreading this negative information the voter is then asked again whether they would still vote for McCain.

The Bush campaign has admitted it does this type of polling, but said that their polls do not use the type of language the woman claimed.

They say the calls are not aimed at stopping people from going to the polls but instead aim to find out what motivates people.

Defenders say that these surveys help campaigns understand exactly what type of information changes people's minds on a candidate.

If they find that a certain fact will turn off voters from an opposing candidate than a campaign commercial may be crafted based around that message.

But opponents say they are used as crude tools of voter suppression, spreading information that is often false and misleading in the hope of keeping voters away from the polls.

Proponents of push polling say that negative politics are a legitimate means of informing voters of the differences between candidates.

Taking the high ground

Critics point out that history shows that the more negative a race is, the fewer people bother to vote.

On February 11th, McCain pulled back from the fight.

In an attempt to regain the high ground he said he would not run any more negative ads.

The calculation was simple - if he was to win, McCain had to draw independents to the polling booths.

These were exactly the people turned off by the type of negative attacks and mudslinging the race had descended into.

The tactic is risky though - it has left Bush and his allies slamming McCain day after day on TV, on the radio and online with almost no comeback.

McCain won in New Hampshire by touring the state and holding 114 Town Hall meetings, drawing in new voters into the primary process.

Politics in South Carolina is a different game altogether.