What is the test for appointing counsel to represent an indigent civil litigant?

Under 28 U.S.C. Sec. 1915(d), the district court has discretion to appoint counsel to represent an indigent civil litigant. Counsel should be appointed under section 1915(d) only in "exceptional circumstances." See Wilborn v. Escalderon, 789 F.2d 1328, 1331 (9th Cir.1986). "A finding of exceptional circumstances requires an evaluation of both 'the liklihood of success on the merits (and) the ability of the petitioner to articulate his claims pro se in light of the complexity of the legal issues involved." Id.