You are living in one of the states of the USA that is staging a Republican primary election. You turn on the television and soon the advertisements begin to roll. But there is something different about them. During the few weeks of the primary campaign, most of them are political advertisements. You watch the candidates cheerfully attacking each other in colourful terms. If you want to watch TV, you cannot escape from the election. That is what the residents of the 10 states that staged primary elections on Tuesday have just experienced.

To put it bluntly, candidates use advertisements to try to destroy their opponents. As The New York Times said of Mitt Romney, the leading contender, he is "extremely adept at defining, diminishing and disqualifying a serial cast of challengers through relentless attacks". Negative ads have accounted for nearly half of the money spent so far on broadcast television during this election.

Nothing on this scale has happened before. It is a result of a change in the law. Supporters of candidates may form what is known as a political action committee (PAC). Provided the committee is operated correctly, it can raise unlimited sums from individuals, corporations, unions and other groups that may be spent on political advertising. These so-called super-PACs must act independently and not collaborate with the candidates they support. In particular, strictly speaking, the candidate must not "request, suggest or assent" to an ad produced by a super-PAC on his or her behalf.

So far as the attack advertisements are concerned, each candidate must be able to take it as well as to hand it out. The super-PAC supporting Newt Gingrich has recently posted linked advertisements mocking Mr Romney. In the first, viewers were asked whether they really know Mitt Romney. "Think again", they are urged. This follows references to Mr Romney's "contradictions", his "tax returns", his business in the "Cayman Islands", his "$100 million" pension plan, his use of a "Swiss bank". He is described as a "serial" flip-flopper and, worst insult of all, as a "progressive" and, as evidence, a picture of Mr Romney with the late Senator Edward Kennedy is shown.

Then comes the second barrel of the attack on behalf of Mr Gingrich, "Blood Money, Mitt Romney's Medicare scandal". The crime, it asks? Medicare fraud. The victims? American taxpayers. The boss? Mitt Romney. "Romney supervised a company that was guilty of massive Medicare fraud... that's a fact", it is alleged. "Romney pocketed $500,000." Cost to the taxpayers? $40m. The sign-off line is – "Mitt's blood money".

I don't argue, however, how dreadful this is and pray that nothing like it crosses the Atlantic. The point about the negative ads themselves is that they are not fiction. They are based on what the candidates have said and what they have done. True, they present the "facts" in the worst possible light and leave out mitigating circumstances. As far as "Mitt's blood money" is concerned, for example, the candidate was indeed running the management consulting firm, Bain, when it did indeed purchase and manage the Damon Corporation, which did indeed defraud Medicare on a grand scale. However, there is no evidence that Mr Romney was personally implicated.

Moreover, provided that a candidate is putting forward policy positions that strike a chord with a sufficient number of wealthy donors, he or she can remain in the race for much longer than used to be the case. Under the old rules, for instance, Mr Romney would probably by now have secured the nomination or be facing Rick Santorum alone, but instead he must continue to fight not only Mr Santorum, but also Mr Gingrich and Ron Paul, each of whom retains ongoing super-PAC support.

I see this extension of the primary election season as an advantage because it strengthens what has always been an impressive feature of the process for electing a US president, the prolonged exposure of the candidates to the electorate. Campaigning begins in January and ends on the first Tuesday after the first Monday in November, this year 6 November.

The activities of the super-PACs provide a second advantage: they empower protest candidates, such as, this time round, Mr Paul. Now 77, he has served in Congress and believes, for instance, that "the proper role for government in America is to provide national defence, a court system for civil disputes, a criminal justice system for acts of force and fraud, and little else". It is, therefore, impossible to be more conservative than Mr Paul. He remains, however, in the race. From this, it follows that super-PACs confer a third advantage. They diminish the power of the parties. They cannot "fix" the election, as they would doubtless like to do.

Could we achieve the same effect? Super-PACs could not exist in our parliamentary system. But by using the internet creatively, we, too, could undercut our traditional political parties. We might not find a "Ron Paul" but we could open up the system.

a.whittamsmith@independent.co.uk