I thought this had been killed-off when the creationists lost in an American court at the Dover trial. Unfortunately I still see and hear from people who insist that ID is a legitimate scientific theory, and that it should be taught alongside evolution.
I have spent a great deal of time researching and writing about Intelligent Design, and I am fairly confident that what I am about to write is accurate.
To understand where this 'theory' came from we need to look at the historical context.
Ultra-conservative religious groups in the US have been trying to stop the teaching of evolution is US schools for about a century. In 1925 the first court case on the issue was heard in Tennessee, where the Butler Act made it illegal to teach evolution in state funded schools. The trial became famous as the 'Scopes Monkey Trial'. Teaching evolution in Tennessee remained illegal until 1967 when the legislature, fearful that another challenge was about to be launched, repealed the Butler Act.
In 1967 the Supreme Court made a crucial ruling (Epperson v. Arkansas about the Akansas equivalent of the Butler Act. The court held that prohibition against the teaching of evolution was unconstitutional - specifically that it violated the Establishment Clause of the First Amendment. Until this time the generally understood position was that the constitution prohibited any state law aimed at establishing a state religion. This new ruling widened this to prohibit any state laws that furthered religion. The court also held that creationism was a religious position, and ,therefore, any law requiring it to be taught alongside evolution was unconstitutional.
The creationists then switched tactics slightly and introduced a law in Louisiana which required public schools to give "equal time" to "alternative theories" of origin. They hoped that by avoiding any direct mention of creationism they could get around the court decision. There was a concerted effort to push something called 'Creation Science' - an attempt to put a gloss of scientific respectability around the religion creation myth. In reality creationists were not doing any proper science - as is easily seen if one looks for published papers in the peer-reviewed scientific journals - the accepted method of introducing any new scientific ideas or challenges. Creationists couldn't get their 'papers' into the journals for the simple reason that they weren't science.
In 1987 the Louisianan law came before the Supreme Court (Edwards vs Aguillard). The court held that the law was unconstitutional. Everything that has happened since needs to be seen in this context.
The Young Earth Creationist lobby1, now led by the leaders of the Discovery Institute, has a stated aim of replacing the teaching of evolution in public schools with the 'truth' of the Christian creation myth. This group cannot be dismissed as a bunch of cranks who pose no real threat. They are extremely well funded and, according to which polls you trust, they represent at least some of the religious views of a very large number of US citizens (between 5 and 50 percent believe in Young Earth Creationism. More information on this here). The National Council for Science Education (NCSE) put the figure at around 10%, which I am inclined to accept. That equates to around 31 million people. A further even more substantial number reject evolution and opt for a creationist position somewhere short of the YEC position. By any measure this is a significant lobby group. Couple this to the fact that they have repeatedly demonstrated that they are comfortable using deception and dishonesty to further their aims2 and you have a very dangerous extremist lobby in the most powerful nation in the world.
1 Young Earth Creationists believe that the Genesis account, in the Hebrew Bible/Old Testament, is a literal and historically accurate account of creation. They believe it occurred according to the calculations of Bishop James Ussher (1581-1656) who used the bible to calculate a date for creation - Sunday 23 October 4004 BCE. (I kid you not).
2 Time and again the YECs have lied to the public, lied to officials and even lied to the courts. This is on the record, as, for example, with the findings of Judge Jones in the Kitzmiller trial. In his summary Judge Jones noted that:
"ID's backers have sought to avoid the scientific scrutiny which we have now determined that it cannot withstand by advocating that the controversy, but not ID itself, should be taught in science class. This tactic is at best disingenuous, and at worst a canard. The goal of the IDM is not to encourage critical thought, but to foment a revolution which would supplant evolutionary theory with ID."
"The citizens of the Dover area were poorly served by the members of the Board who voted for the ID Policy. It is ironic that several of these individuals, who so staunchly and proudly touted their religious convictions in public, would time and again lie to cover their tracks and disguise the real purpose behind the ID Policy."