Addressing a poll rally in Karachi, the 65-year-old cricketer-turned-politician claimed that a "big game" is being played to hurt the credibility of the general elections and Nawaz Sharif and others are behind this "conspiracy".
According to police officer Zahoor Afridi, the candidate Ikramullah Gandapur from opposition leader Imran Khan's party, was returning home from a campaign event when the bomber struck in the city of Dera Ismail Khan, wounding him.
Pakistan's top court on Sunday said it had begun reviewing statements made by a judge alleging the country's spy agencies were influencing judicial proceedings, as the powerful military called for an investigation. The Pakistani Taliban claimed responsibility for the attack in a message sent to the media.
Pakistan Tehreek-i-Insaf chief Imran Khan has condemned the attack.
The attack followed a suicide blast in the southwestern province of Balochistan on July 13 which killed 149 people, underscoring continuing security challenges in Pakistan following years of dramatic improvements.
A massive suicide bombing at a rally in Mastung in the south western province of Baluchistan province, killed Siraj Raisani along with 148 people.
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Sunday's attack targeted the vehicle of Ikramullah Gandapur, a candidate of the Pakistan Tehreek-e-Insaf (PTI), or Pakistan Justice Movement, after he was leaving a political meeting, two police officials told Reuters.
Violence in Pakistan has dropped significantly since the country's deadliest-ever militant attack, an assault on a school in the northwestern city of Peshawar in 2014 that killed more than 150 people, a lot of them children.
Gandapur was the former agriculture minister of Khyber Pakhtunkhwa. "It is a big conspiracy against the state of Pakistan", he added.
Durrani survived a suicide attack earlier this month that killed four people.
The Pakistan Muslim League-Nawaz, which took power in 2013, hopes for a new mandate under leader Shahbaz Sharif, a brother of the ousted Nawaz.
Voting for those two seats would take place at a later date.