Anyone who watches Court TV or "Law & Order" knows this: Once a lawyer or witness opens the door to a particular issue or line of questioning, it can be tough to close it again.

Say a witness claims he's an honest man, doesn't drink or never cheated on his wife. The judge is likely to let the other side challenge that assertion. And if the first lawyer objects -- "Your honor, this man is not on trial!" -- the judge may point out that the witness opened the door himself.

The same principle applies outside the courtroom. After presidential candidate, U.S. Sen. John Kerry made a big deal at the Democratic convention about his military service in Vietnam while giving short shrift to his years in the Senate, Republicans declared his war record fair game and went after his Swift Boat claims with a vengeance. They may well have done this anyway, and with just as little regard for the truth, but Kerry was in no position to cry foul since he put the issue on the table to begin with.

Now we are at a similar place with Harriet Miers, President Bush's lawyer, close friend and choice to succeed retiring Justice Sandra Day O'Connor on the Supreme Court.

Ms. Miers was a faith-based nominee on two levels. In introducing her to the American people, Mr. Bush cited her religious faith as a principal qualification for the high court. He also expected his right-wing Christian base to take it on faith that her faith guaranteed she'd cast the votes they have long been seeking on hot-button culture issues from abortion and gay rights to the separation of church and state.

Clearly, the president expected fellow conservatives to understand the code. Ms. Miers was a stealth candidate, someone whose blank-slate record would give the opposition few grounds for objection, but whose religious values would pass the litmus test that everyone pretends doesn't exist.

He figured wrong.

Ms. Miers was an unknown Bush buddy, and his record of good-buddy hires thus far has been a monument to incompetence. She may be a notable exception, but how was anyone to judge that? She had no record of judicial rulings, legal opinions or scholarly writings.

Now comes a document proving her bona fides. In 1989, as a candidate for the Dallas City Council, Ms. Miers pledged staunch opposition to abortion, giving the "correct" answer to all 10 questions posed by the anti-abortion group Texans United for Life. Among other things, she promised to back a constitutional amendment banning the procedure and to appear at "pro-life rallies and special events."

So much for the blank slate. Presidential spokesman Scott McClellan said his boss knew of these views before he picked Ms. Miers (no kidding), but that Mr. Bush "did not discuss with her or anyone else whether or not those were still her views."

So the mystery, to the extent it existed, is over. But the door to Ms. Miers' religious beliefs remains wide open, and Mr. Bush opened it himself. When that didn't work right away, he took the door off its hinges and finally demolished the whole wall. How else to describe his recruiting of James Dobson, icon of the Christian right, to vouch for Ms. Miers based on inside information he "probably shouldn't know."

Now neither one of them is in a position to claim religion off-limits, and Senate committee members had better recognize that. If they don't ask some pointed questions and demand some concrete answers, they'll look like even bigger idiots than they did during John Roberts' hearings, where self-serving blather was their distinguishing characteristic.

Until this week, it could have been argued that Ms. Miers was not responsible for what the president and others have said about her. But now, in addition to the Texas document, there is something else to explain -- namely, the bizarre back-and-forth she had with Republican U.S. Sen. Arlen Specter.

As chairman of the Judiciary Committee, Mr. Specter met for almost two hours with the nominee. Afterward, he said she told him that she believes the U.S. Constitution contains a right to privacy, and that two important cases to that effect were correctly decided by the court. The right to privacy, of course, was established in a case that made it legal to use birth control. It is also the load-bearing pillar on which a woman's right to abortion currently depends.

Mr. Specter said he considered those statements key indicators of the nominee's judicial philosophy. But hours later, a White House spokesman disputed the senator's take on the conversation, and Ms. Miers called him to say he had misinterpreted her remarks. That led his spokesman to issue a bizarre retraction, saying that his boss "accepts Ms. Miers' statement that he misunderstood what she said."

Is Mr. Specter confused, exceedingly dense or prone to hearing only what he wants to hear? Did the nominee make vague, contradictory statements or speak in a code that he failed to decipher? Or did she try to have it both ways, assuaging his doubts and then denying it?

A nominee who sees no right to privacy in the Constitution might be just the ticket for Rick Santorum, who has said the same thing, but most Americans do not want government telling them what they can and cannot do in the most private areas of their lives.

Judiciary Committee members need to get to the bottom of this. And they can start by forgetting all that stuff about religion being off-limits.

Up until now, any senator questioning a nominee's faith might have looked like bigot, but now the rules have changed.

The president opened that door himself, and the committee darn well better have the guts to walk through it.

Faith-based nominee can't evade religious questions