Azad Samaj Party founder Chandrashekhar Azad allegedly received a death threat, a party office-bearer said on Thursday and added that a police complaint has been lodged.
A case has been registered at Qutubsher police station and an investigation is underway, police said.
Azad is contesting the Lok Sabha elections from the Nagina constituency.
Karanveer Singh, the Azad Samaj Party's district unit chief, said he received a call around 6.30 pm on Tuesday, with the caller using "abusive language" against "great men".
Singh claimed the caller also used "casteist slurs".
The caller then issued a threat, saying Azad had survived an earlier attempt on his life after being shot in Deoband as the gun was fired by his aunt's son but will not survive this time.
Singh said he informed the Senior Superintendent of Police (Saharanpur) Vipin Tada and gave a memorandum demanding the culprit's immediate arrest.
Superintendent of Police (City) Abhimanyu Manglik told PTI that a case has been registered and action will be taken after a probe into the allegation