THE RELUCTANCE OF Marvin Mandel and his wife, Jeanne, to relinquish his governorship was understandable; it is never pleasant to concede incapacity. Moreover, as we have noted in this space previously, we were not among those who felt that Mr. Mandel had to step aside merely because of charges pending against him. Our reasons had to do with his health and the interest of the state - and it is on these grounds that we now welcome the decision to transfer all formal powers of the office to Blair Lee III "until I am pronounced fully able to resume the duties and obligations of my office."

That is precisely what the voters of Maryland provided for in 1970, when they amended the state constitution to establish the office of lieutenant governor who, among other duties, "serves as acting governor in case of the governor's disability." Last Wednesday, after 22 days of hospitalization and the postponement of his retrial, the governor appeared in court in obviously weak condition. At that point, there could no longer be any serious question about the need to invoke the constitutional transfer-of-power provision.

Certainly, Acting Gov. Lee knows what the job entails. Indeed, he is in somewhat awkard position, for his desire to be governor has been no secret in the past. At the same time, he has been a vigorous lobbyist and articulate spokesman for the Mandel administration. Now he must try to mesh some of Mr. Mandel's wishes for future appointments and certain other policy desires with his own decisions as leader rather than puppet.

So it is only human for Gov. Lee to relish his new status. Yet given the events that led to it, he may find it wise to temper his exuberance with some circumspection. Besides, the others in the field hoping to win the governorship next year will no doubt be giving his provisional administration special scrutiny.

Mr. Mandel has stated that he has "every assurance from my physicians that full restoration of the vigorous health I enjoyed before my illness can be accomplished through an adherence to the scaled-down regimen that has been prescribed for me." Surely all Marylanders join us in wishing him a full recovery.