delegitimize       
verb [ T ]  formal uk/ˌdiːləˈdʒɪt.ə.maɪz/ us/ˌdiːləˈdʒɪt̬.ə.maɪz/ (UK usually delegitimise)
 (使)失去合法性
to make something seem not valid or not acceptable
  If he does not take part in the election, it would delegitimize the entire electoral process. 如果他不参加选举,整个选举过程就会失去合法性。 
 - More examples
 - His spokesmen raged against the news media to delegitimize critical stories.
 - She argues that nationalism was engrained in the very system of colonialism that it sought to delegitimize.
 - The government’s tactics have been to delegitimize the voices of the poor.
 - The intelligence agencies will try to use this to delegitimize the authenticity of the evidence that the captain was murdered.