At least 128 people, including Raisani, were killed in the deadly blast, police officials said. Raisani was a candidate from PB-35 (Mastung) and his elder brother Nawab Aslam Raisani had served as the province's chief minister from 2008 to 2013.
It was the second election-related violence to occur on Friday.
The pair arrived from London, where they were visiting Sharif's ailing wife when a Pakistani court convicted them of corruption.
He was taken into custody but is expected to appeal his sentence and seek bail.
Former prime minister Benazir Bhutto was killed in a bomb-and-gun attack after an election rally ahead of 2008 polls.
His son-in-law is now serving his one year prison sentence on the same charge, which stems from the purchase of luxury apartments in Britain, which were found to have been bought with illegally acquired money.
Barricades and barbed wire were placed across roads toward the airport to prevent crowds.
Earlier, minor attacks on the houses and convoys of election candidates have taken place in different parts of Balochistan.
Sharif has been banned from participating in politics, and his brother Shahbaz Sharif now heads his Pakistan Muslim League and is campaigning for re-election on July 25.
At least 72 people were killed and 120 were injured in the attack during a campaign rally in Mastung.
In February 2017, Islamic State claimed responsibility for a suicide bombing at a shrine in southern Pakistan, killing 83 people and wounding over 150.
Hawks acquire Jeremy Lin from Nets
Lin, 29, played in only one game last season with Brooklyn, sustaining a season-ending ruptured patellar tendon on opening night. According to Wojnarowski, however, league sources said they expect the Hawks to now trade Schroder this offseason.
During his term in office, Sharif criticised the military's involvement in civilian affairs and its efforts in fighting extremists.
He may have been targeted amid ongoing allegations that Mr Sharif is being kept out of politics to allow the military to maintain power.
There are fears of more violence in the run-up to polling day.
Earlier in the day, a suspected suicide bomber rammed his explosive-laden motorbike into a vehicle minutes after the end of an election rally in the remote Bannu district, bordering the restive North Waziristan tribal region, killing five people and injuring another 30.
Durrani, the JUI-F central general secretary, is contesting for the upcoming polls from the Muttahida Majlis-e-Amal (MMA) platform, against Pakistan Tehreek-e-Insaf (PTI) Chairman Imran Khan.
Akram Khan Durrani, a former CM of Khyber-Pakhtunkhwa, remained unhurt in the attack. Picture: EPAMr Raisani died at a hospital in Quetta, the capital of Baluchistan province, hours after being critically wounded.
Another 45 people were hurt in the attack in Mastung, a town in southwest Baluchistan province.
Mr Khan, who hopes to become the next prime minister, condemned Friday's attack against his opponent, Mr Durrani.
"It seems the target of the suicide attack was Siraj Raisani", a senior police officer said.
Earlier he had also confirmed that the blast was carried out by a suicide bomber and that the explosion had killed Siraj Raisani, who was running for a provincial seat with the newly formed Balochistan Awami Party (BAP).