Suppose Richard Nixon had ordered Attorney General John Mitchell to subpoena Washington Post reporters Bob Woodward and Carl Bernstein and had found a judge to order them to reveal their sources, especially “Deep Throat.”

Almost certainly, Woodward and Bernstein would have gone to jail rather than unmask Woodward’s chief source, now known to be then-Deputy FBI Director Mark Felt. But Felt and other informants might well have been scared off from talking to the journalists. Nixon conceivably could have survived Watergate, and American history would be the worse for it.

That possibility — and not the inflamed partisanship surrounding the current CIA leak controversy or attitudes toward the media — should guide Congress as it considers legislation to shield reporters from having to disclose their sources in federal cases. As one of the measure’s chief sponsors, conservative Republican Rep. Mike Pence (Ind.), puts it, “This is not about protecting reporters. This is about protecting the public’s right to know.”

The public’s right to know across a range of issues — from mere candid opinions on a dicey political situation to petty corruption to concealment of records all the way to potential high crimes and misdemeanors — often depends on confidential sources who won’t cooperate with the media if they fear exposure.

Thirty-one states have adopted legislation shielding journalists from being forced to reveal sources, and in 18 others, courts have erected a shield. The Justice Department’s guidelines provide that prosecutors can’t try to subpoena journalists without the attorney general’s express permission except to avoid a loss of life or protect the national security.

However, the guidelines do not apply to special prosecutors or civil cases. It’s Special Counsel Peter Fitzgerald, of course, whose subpoena in the CIA leak case led to the imprisonment of New York Times reporter Judith Miller. But more than two dozen other reporters around the country have been threatened with jail in the past year in four different federal jurisdictions, according to another shield sponsor, Sen. Dick Lugar (R-Ind.).

Lugar and Pence both testified before the Senate Judiciary Committee in July, and Pence aides say that Chairman Arlen Specter (R-Pa.) is favorably disposed toward moving the legislation when Judge John Roberts’ confirmation hearings are concluded. House Judiciary Chairman Jim Sensenbrenner (R-Wis.) is also said to be supportive, but the Bush administration’s stance is problematical.

Even though House and Senate sponsors amended their bills to provide that reporters would not have an absolute shield — especially when national security is at stake — Deputy Attorney General James Comey declared in a statement that the legislation was “bad policy” because national security could be endangered. There’s no justification for administration opposition now. Congress should pass the bill.