Seven would-be candidates for local and county offices failed to show their constitutional rights are being violated by a requirement that they collect more voter signatures than their counterparts seeking statewide office, a federal judge held.In a written opinion last week, U.S. District Judge Elaine Bucklo denied a motion to place the candidates — one each for Cook County sheriff and assessor and five for commissioner of the Metropolitan Water Reclamation District of Greater Chicago — on the ballot in the Democratic …