What is the test for a motion to replace a defense counsel at trial?

at p. 694.)³³ He was, however, required to establish that a failure to replace defense counsel would substantially impair his right to the assistance of counsel. (People v. Smith, supra, at pp. 690-691.) It is not enough for a defendant merely to show trial counsel could have done something differently. "A series of attorneys presenting groundless claims of incompetence at public expense, often causing delays to allow substitute counsel to become acquainted with the case, benefits no one. The court should deny a request for new counsel at any stage unless it is satisfied that the defendant has made the required showing. This lies within the exercise of the trial court's discretion, which will not be overturned on appeal absent a clear abuse of that discretion." (Id. at p. 696.)