More than just Robert Gates will in effect be on trial when his nomination as the new head of the CIA comes before the Senate for confirmation.

Also on trial will be the ability of the Senate to conduct confirmation hearings fairly and fully without turning them into an attempt to settle old scores and resolve old doubts left over from the Iran-Contra scandal.The temptation for partisan grandstanding is bound to be great. Some lawmakers aren't convinced that Gates told all he knew about Iran-Contra. Others wonder if Gates acted vigorously enough when he was deputy CIA director in the Reagan administration and started being suspicious of wrongdoing in that scandal. Still others seem eager to use any opportunity to embarrass President Bush by reminding the country of unanswered questions about his possible role in Iran-Contra as Reagan's vice president.

But it's hard to imagine that an investigation into Gates' confirmation could uncover much, if any, information about Iran-Contra not already unearthed by the previous probes into that scandal. Special prosecutor Lawrence Walsh hasn't been able to dig up any dirt on Gates, who testified only a few days ago before the continuing Iran-Contra grand jury. At no time has Gates ever been implicated in the diversion of arms sales profits to the Nicaraguan rebels.

Besides, when it comes to assessing his fitness to direct the CIA, Gates' performance in his current assignment, as deputy national security adviser, ought to matter more than such comparatively ancient history as Iran-Contra. On this score, the evidence is impressive.

As a day-to-day overseer of the National Security Council staff, Gates is credited with guiding the administration's foreign policy decisions in such key crises as those in the Persian Gulf and Panama and in shaping U.S. relations with the Soviet Union. Though plenty of cooks helped bake those dishes, the success of these policies is at least some indication of the soundness of Gates' judgment.

In his present job, Gates has developed a reputation as a professional determined to carry out his duties without pushing a personal agenda - a fault attributed to some CIA chiefs in the past.

Before his current assignment, Gates spent more than 20 years at the Central Intelligence Agency, rising through the ranks as a specialist in Soviet affairs.

If confirmed in his new nomination, Gates would take over a CIA considerably improved by his predecessor, William Webster, but still facing plenty of headaches and challenges. The latest line of criticism is that the intelligence community should have done a better job foreseeing Iraq's intention to invade Kuwait, judging its military capabilities once the Persian Gulf war started, and assessing Saddam Hussein's ability to survive post-war rebellions.

In assessing Gates' fitness for the new post, the Senate would be well advised to avoid the temptation to dwell lengthily on old quarrels and focus instead on how best to build on the solid foundation that Webster left at the CIA.