The latest personal scandal to afflict President Clinton is potentially the most important of the issues being examined by the criminal prosecutor investigating him. If the alleged sexual affair between the president and a young White House aide, Ms Monica Lewinsky, is shown to have occurred, there is nothing illegal, but much that is reckless about it, given the popular and media preoccupation with politicians and sex.
What makes it potentially disastrous for the president is the suggestion that he asked her to commit perjury by lying to lawyers acting for Ms Paula Jones, who is suing him for sexual harassment, and the existence of potential proof that he did so. Mr Clinton has furiously denied the charges, but if it is shown that they are true, it would expose him to impeachment proceedings from the House of Representatives. Given the depth of feeling he provokes from many of his Republican antagonists, it is not surprising that such an outcome is suddenly being discussed seriously in Washington.
It is obviously preoccupying the president and his staff, just when he is preparing his State of the Union address for delivery next week, and in the midst of the most sensitive negotiations over the Middle East peace process. Anything that so diverts executive attention diminishes its power. Those who are relying on firm US action over coming months - not least concerning the Northern Ireland peace process - will worry that a protracted scandal, with a drip feed of leaks, will weaken the capacity for constructive involvement.
Clearly it is too early to say whether this will be the case. The legal process takes time to work through and there is much that is murky about the latest allegations. But it cannot be denied that due legal process has so far been scrupulously followed. A three-judge panel, headed by the US Chief Justice, Mr William Rehnquist, authorised the Whitewater investigator, Mr Kenneth Starr, to expand his investigation into these latest allegations, after Ms Janet Reno, the attorney-general, forwarded his request to do so last week.
It is a tawdry affair, which would certainly not deserve the attention it is getting were it not associated with other investigations. If it seems astonishing that Mr Clinton could have been so reckless, it is not the first time that powerful politicians, several of them among the most distinguished residents in the White House, have been associated with extra-marital affairs. There may be a psychological assumption of invulnerability tempting some of them to take such risks. It is all the more surprising in this age of media intrusiveness and prurience into matters personal and sexual.
There is, however, no doubt of the short and potentially long-term damage the affair can do to Mr Clinton, not least to the dignity of his office. The immediate opinion polls show that a majority of US voters still incline to believe Mr Clinton's account of the matter, but is convinced the perjury charge must be taken very seriously. It is the possibility of providing proof one way or another that differentiates this from the other cases that have dogged Mr Clinton's term in office.