Harrisburg, Pa. ? Fictional presidential candidate Matt Santos on NBC’s “The West Wing” recently discussed it, as did real-life President George Bush in the White House, not to mention “The Daily Show” host Jon Stewart, more than three dozen Nobel laureates and numerous school boards across the country.

A decade ago, most Americans had never heard of intelligent design, or ID. But, in the past year, the term has surfaced repeatedly in politics, media and education as the rallying point for religious conservatives in the spreading culture war over the teaching of Charles Darwin’s theory of evolution.

Although polls show about half of Americans still don’t recognize the expression, the background and meaning of ID are focal points of a landmark First Amendment case unfolding in Pennsylvania’s capital.

A very old phrase that gained new currency about a decade ago, ID presents itself as an alternative scientific theory to evolution. It posits that some aspects of the natural world, yet unexplained by Darwin, suggest design by an unnamed intelligent agent.

The prime engine propelling the dissemination of ID is the Seattle-based Discovery Institute, a think tank whose $4 million budget is heavily funded by conservative Christian donors. Discovery’s Center for Science & Culture (formerly the Center for the Renewal of Science and Culture) laid out its goals in a 1999 fundraising document called “The Wedge Strategy.”

Determined to drive a “wedge” into the tree trunk of “scientific materialism,” it said, “Design theory promises to reverse the stifling dominance of the materialistic worldview, and to replace it with a science consonant with Christian and theistic convictions.”

Former Dover, Pa., school board member Bill Buckingham, right, is escorted by a supporter as he leaves the Federal Courthouse on Thursday in Harrisburg, Pa. Buckingham, a former school board member, denied advocating that creationism be taught alongside evolution until lawyers in a courtroom played a news clip that recorded him making such a comment.

John West, associate director of the Center for Science & Culture, pointed out that the wedge proposal was a plan, not a scholarly document.

“That document was about more than intelligent design. It was about the larger cultural context and the anti-religious agenda of some people in the name of science,” he said.

Pennsylvania is the first state to see ID included in a district curriculum, but Ohio and Minnesota and at least one district in New Mexico include critical analysis of evolution in their science standards. Kansas is expected to do so this fall. More than 24 state and local authorities have considered similar changes to their science curricula over the past year, according to the National Center for Science Education, a California-based nonprofit group dedicated to defending the teaching of evolution in public schools.

A week ago, intelligent design made its European debut in Prague, Czech Republic, at an international scientific conference drawing 700 attendees from Europe, Africa and the United States, according to The Associated Press. Many of those who spoke at “Darwin and Design: A Challenge for 21st Century Science” were from the Discovery Institute, including Stephen Meyer, the Cambridge University-educated director of the Center for Science & Culture.

ID is “creationism in a cheap tuxedo,” according to Leonard Krishtalka, director of the Kansas Museum and Biodiversity Research Center at Kansas University.

Not so, said William Dembski, a Discovery fellow and leading ID proponent, who directs the Center for Science and Theology at Southern Baptist Theological Seminary in Louisville.

“Creationism was consciously trying to model the science on a certain interpretation of Genesis. You don’t have anything like that in intelligent design,” said Dembski, who holds doctorates in mathematics from the University of Chicago and in philosophy from the University of Illinois and a master of divinity degree from Princeton Theological Seminary.

Whether ID is a scientific theory or a religious belief is at the heart of the First Amendment case Kitzmiller v. Dover Area School District in central Pennsylvania, the apparent inspiration for “The West Wing” script in October.

Parents of Dover students sued the district and school board over a requirement that ninth-grade biology students be informed of ID as a scientific alternative to evolution. The parents, who claim that ID is creationism in disguise, contend that such a requirement is religiously motivated, thus violating the separation of church and state.

Attorneys for the school district argue ID is not a religious belief but a valid scientific theory and that the school district intended only to expose students to views critical of and differing from evolution. The case, in its sixth week, may influence how biology is taught in public schools around the country.