His appointment is an interim appointment and expires in January, 2010, after a special election is concluded.
UPDATE: A Republican challenge to the appointment has been rejected in federal court. The Republican party contended that Governor Patrick lacked the authority to expedite the appointment. The appointment was made under a new law passed this week giving the Governor the power to appoint an interim Senator until the special election, but under Massachusetts law new legislation takes 90 days to go into effect. The Governor can declare a law an emergency and implement it immediately, as was done in this case. The Republican Party argued that this power was not absolute and the use of it in this case would do irreparable harm. Judge Connolly denied the request for an injunction saying “The (Republican) Party has not shown that it has a chance to succeed on the merits and, therefore, any risk of harm to the party will not outweigh the risk of harm to the governor and the commonwealth.”