Washington ? This is a week of celebration for two of Washington’s great dissenters on the right. On successive nights, dinners are honoring Edwin Feulner for his 25 years at the helm of the Heritage Foundation and Edward Crane for his role in founding the Cato Institute a quarter-century ago. The success of their think tanks is something to cheer, even if, as is my case, you often disagree with their policy prescriptions.

To appreciate what they have achieved, you have to recall that in 1977, when Feulner left his congressional staff job to run the four-year-old Heritage (which he had helped found) and when Crane started Cato out in San Francisco, Jimmy Carter had just been inaugurated and Democrats controlled both houses of Congress. “It was not a hospitable time for Republicans, let alone conservatives,” Feulner recalled.

Today, with Republicans running the White House and the House of Representatives and one vote away from regaining control of the Senate, it is easy to see the triumph of conservatism as a historical inevitability. It was not. The political victory can be credited largely to Ronald Reagan. But it was also an intellectual battle, in which Heritage and Cato, along with the older American Enterprise Institute, played a critical role.

Heritage and Cato have become so proficient in generating and promoting ideas that the liberal movement has had to create its own think tanks to compete. With generous corporate and foundation support and thousands of grass-roots contributors, Heritage boasts a staff of 185 and a budget of $28 million; Cato, 98 staffers and $16 million.

In their headquarters buildings, Heritage on Capitol Hill and Cato in a handsome modern structure closer to the White House, they sponsor a steady stream of conferences and churn out papers and books, nudging and prodding the policy-makers and opinion-shapers. Feulner has Heritage on hair-trigger, rushing out suggestions before congressional hearings and bill markups. “We sweat the details” critical to the legislative process, he told me. Cato, Crane remarked in a separate interview, “is a little more academic and long-term in its thinking.”

Heritage, which had a foothold in Washington when Reagan arrived, wrote a blueprint for his first term called Mandate for Leadership, which became a kind of handbook for the new administration. Tax cuts, missile defense, enterprise zones for cities and scores of other ideas migrated from Heritage to the White House and Capitol Hill.

Cato, which moved to Washington in 1982, has sponsored legal studies influential in the Supreme Court decisions reviving the 10th Amendment limits on federal authority. At times, their agendas overlap. A central, but still unfulfilled dream of Cato’s since 1979, now shared by Heritage, is the conversion of Social Security into a system of private retirement accounts.

But the two are not twins. Heritage is mainstream conservative, emphasizing free-market economics and robust national security policy, with some forays into social policy on health care and welfare reform. Cato is libertarian in its roots, more radical in its critique of federal programs, more skeptical about the U.S. international role and decidedly liberal (in the classic sense) on issues of personal freedom and civil liberties.

Their usefulness in Washington politics stems from their intellectual honesty and their willingness to question conventional wisdom, even when their friends are in power. A case in point is the bipartisan but outlandishly expensive farm subsidy bill, which President Bush is preparing to sign. Heritage’s Stuart Butler denounced it last week as “a shameless example of corporate pork-barrel spending.” And when the establishment was recently cheering the latest campaign finance “reform,” Cato and Heritage had forums challenging the government’s right to regulate political speech.

In a city noted for the narrowness of its intellectual range, it is sometimes wildly unpopular but absolutely vital to have institutions that question fundamental assumptions and occasionally declare that the emperor of the moment has no clothes. Cato and Heritage do that to Republican presidents as well as Democrats.

They are also models of healthy democratic discourse at a time when too much of the policy debate here takes the form of “Crossfire”-style exchanges of insults. They have staffed themselves with scholars and writers who share their basic political orientations. But their doors are open to other views, and the policy forums they run are not only stimulating but good-tempered.

What Crane told me is true: “The Washington think-tank world is a great example of how people can have a civil discussion and debate. You don’t see it in politics, but politics these days is largely devoid of content.”

As long as that is true, all of us who work here in politics or journalism have reason to be thankful that Heritage and Cato are around.

David Broder is a columnist for Washington Post Writers Group.