(a) Except in the case of a vacancy caused by sickness, the person serving as an acting officer as described under section 3345 may serve in the office—
(b)
(1)
If the first nomination for the office is rejected by the Senate, withdrawn, or returned to the President by the Senate, the person may continue to serve as the acting officer for no more than 210 days after the date of such rejection, withdrawal, or return.