When physicist Bill Foster was contemplating a congressional run in his Illinois home district, he got some helpful advice from others who had made the jump from science to politics. He was told, he says, that he should branch out from science policy and "bring a scientific view to the full range of issues."

Foster, 52, who spent 22 years as a scientist at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., now has his shot after defeating Republican James Oberweis in a March 8 special election to finish out the term of former House Speaker Dennis Hastert (R), who resigned in November. Sworn in on March 11, he joins two other PhDs in Congress—Reps. Rush Holt (D–N.J.) and Vernon Ehlers (R–Mich.)—both physicists.

Democrats hailed the victory—in what has long been a solidly Republican district—as a sign of voter dissatisfaction with the policies of the Bush administration. But the win was also a hopeful sign for scientists who have watched from the sidelines in disbelief as politicians cut science funding and distorted research on evolution, stem cells and global warming.

Foster says he wants to bring his "fact-based" approach to issues such as health care and energy. "As a scientist, the starting point is always the facts of the matter, whereas often in politics the starting point is how does this play in the next election," he says.

He has the scientific credentials to back up his talk: In graduate school at Harvard University in the early 1980s, Foster worked on the IMB (Irving-Michigan-Brookhaven) proton decay detector, a cube of purified water 60 feet (18 meters) wide constructed deep inside a salt mine located under the shore of Lake Erie. Lined with highly sensitive light-detecting tubes, the experiment was designed to test so-called grand unified theories (GUT) of particle physics, which predicted that protons in the water would very rarely split into lighter particles and produce a flash of blue light. Foster's 1983 PhD thesis contained some of the detector's first published data, which ruled out the simplest GUT.

A year later, Foster moved to Illinois to work as a scientist at Fermilab, where he developed software tools that helped researchers sift through mounds of data that in 1995 led them to uncover the long-awaited top quark, the heaviest known subatomic particle. This was the sixth and final quark predicted by a highly successful theory of what goes on inside single protons or neutrons.

He also led a team that designed a new type of high-speed integrated circuit for particle detectors. That design is still being used today, he says, in the new CMS detector—one of two main experiments constructed for the Large Hadron Collider (LHC) near Geneva, Switzerland, the largest particle accelerator ever built—set to switch on and begin hunting for never-before-seen particles later this year.

His biggest achievement, however, was his co-invention of a system for boosting the efficiency of Fermilab's Tevatron. Long the world's most powerful accelerator, the machine smashes together streams of protons and antiprotons moving at near–light speed so researchers can study the subatomic debris for new particles. By collecting and storing antiprotons for reinjection into the main accelerator, the 1.9-mile (3.1-kilometer) Permanent Magnet Antiproton Recycler Ring more than doubled the rate of proton–antiproton collisions the Tevatron could produce, allowing it to stay at the cutting edge of particle physics.

Foster says the switch from physics to politics came naturally, thanks to a "strong recessive gene for political activism." His mother and father met in the early 1950s in Washington, D.C., where they both worked for Democratic senators. His father, who had studied chemistry but switched to law after World War II, helped draft guidelines for school desegregation in the 1960s that were adopted by the federal government in its enforcement of the Civil Rights Act of 1964.

"I grew up in a family that was always talking about politics," Foster says. (His sister's middle name is "Adlai," after the diplomat and liberal icon Adlai Stevenson, a onetime governor of Illinois and two-time Democratic presidential candidate.)

During his years as a physicist, however, he had to put politics on the back burner. "You read the newspaper and see things you don't like," he says, "and you fold up your newspaper and you go and you do your job all day." In 2006, when his daughter Christine, now 20, left home for Stanford University (his son Billy, 24, is a software engineer in Madison, Wisc.), Foster saw his opportunity. "I said, okay, I'm going to try to make a difference."

To learn the ropes, he volunteered to work on the campaign of Democrat Patrick Murphy, an Iraq war veteran running for Congress in Pennsylvania. Foster, served as a "get-out-the-vote" coordinator, writing software that pinpointed swing voter homes that were believed crucial to Murphy's narrow victory.

Foster, like Murphy, ran as a Democrat in a heavily Republican district. His campaign platform called for withdrawing U.S. troops from Iraq, seeking clean energy alternatives, strengthening immigration controls, and providing comprehensive health care coverage. Armed with an endorsement from his state's popular Democratic junior senator and presidential hopeful, Barack Obama, Foster won by a 53 to 47 percent margin.

In addition to Obama, Foster also attracted the backing of many scientists. He secured endorsements from dozens of top researchers, including 28 Nobel laureates. Physicist Gordon Watts of the University of Washington in Seattle announced on his blog that he had contributed $250 to Foster's campaign.

Cosmologist Lawrence Krauss of Case Western Reserve University in Cleveland, one of those who endorsed Foster, says he would like to see more science PhDs in Congress. "We need to at least raise the awareness that there's a connection between science and technology to these issues of the environment, [to] national defense, to energy production, etcetera," he says. "And it's great to have some people in Congress with some [scientific] literacy … who hopefully can provide some perspective."

Foster was elected at a crucial moment for U.S. physics. Congress in December slashed the high-energy physics budget, forcing labs to cancel or curtail ongoing projects such as the design of the International Linear Collider, a planned particle accelerator that would follow up on discoveries made at the LHC. Fermilab announced that, as a result of the federal funding cuts, it would have to lay off about 200 of its 1,940 employees, who are already taking unpaid one-week furloughs every two months for the rest of the fiscal year.

As a freshman in Congress, there may be little Foster can do to help his Fermilab friends, now his constituents. He says he will urge colleagues to provide relief for the lab to prevent layoffs, but he is not optimistic. "I understand clearly as a freshman in Congress you don't get to steer the bus," says Foster, who secured a seat on the House Committee on Financial Services, which deals with issues such as credit card abuse and predatory lending.

Foster sees ways that U.S. science policy could be improved. He says politicians need to understand that large-scale science experiments cannot be stopped and started without disrupting the research as well as the lives and careers of hundreds of researchers, which he says can strangle a scientific field when it happens repeatedly.

Calamitous budget cuts make it all too obvious why scientists should take a more active role in the political process, Foster says. "They are shooting themselves in the foot," by not getting involved, he says. He urges researchers to brush up on congressional policy and keep their representatives informed about their work. "You do get listened to," he says. Or in some cases, elected.