THE DEATH Tuesday of Senator Edward M. Kennedy puts Massachusetts at half strength in the US Senate at a precarious time. Massachusetts lawmakers will only worsen the situation if they fail to take steps to assure a timely replacement.

Kennedy anticipated the problem. Fearful that the Senate would lack a key vote on major bills, he urged state legislators in a letter shortly before his death to change state law to allow a temporary appointment by the governor - with the assurance of an “explicit personal commitment’’ that the appointee would not run for the office a few months later. It is a sensible solution that enjoys Governor Patrick’s support, and a practical one, too, provided the Legislature can act in time. In 2004, state lawmakers foolishly...