What is the test for setting aside a union election in violation of section 401 of the Civil Rights Act?

Section 402(c) provides that where, as here, a union election is found to have been conducted in violation of 401, the court must set aside the contested election and direct that a new election be held under the supervision of the Secretary and in conformity with the constitution of the union and the requirements of Title IV of the Act. See Trbovich v. United Mine Workers, 404 U.S. 528, 537 n. 8 (1972).