Pakistan’s secular politicians are facing a wave of vicious Taliban shootings and bombings that have killed candidates and their supporters as part of a dangerous election season that some fear could tilt the electoral field against moderate voices.

The Pakistani Taliban has threatened to attack members of the Awami National Party (ANP), the Muttahida Qaumi Movement (MQM), and the Pakistan People’s Party (PPP). All three parties describe themselves as liberal and were part of the outgoing ruling coalition that governed Pakistan for the past five years.

Since the start of campaigning, the ANP has faced at least six major attacks. On 16 April, a suicide bomber killed 16 of their supporters when he blew himself up outside a party meeting. One of its party leaders, Ghulam Ahmed Bilour, escaped with minor injuries. The target of the attack was his nephew, Haroon Bilour, whose father, an ANP provincial minister, was assassinated last December.

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“This is pre-poll rigging,” said Bushra Gohar, a former ANP parliamentarian. “The Taliban are trying to get the secular liberal parties [out of parliament].” Members of the secular parties say the perilous campaign conditions have reduced their efforts to door-to-door campaigning while surrendering a wider field to their rivals in Islamist and right-wing parties.

The deteriorating security situation affects all politicians who have backed Pakistan’s military operations against the Pakistani Taliban. A bomb was discovered today by the Islamabad police under a car near the residence of former military ruler Pervez Musharraf, who is currently being held under house arrest on charges of illegally detaining judges when he imposed a state of emergency in 2007.

A bomb disposal squad was called to Mr Musharraf’s house outside Islamabad. It is unclear who was responsible for placing the explosives there. His hopes of a return to power in the country’s 11 May elections were dashed earlier this month when judges disqualified him from running. The retired dictator has been threatened by the Taliban, which paraded a death squad in a video, when Mr Musharraf returned to Pakistan after four years in exile last month.

In light of the security threats, the secular parties have had to avoid major political rallies, a hallmark tradition of south Asian politics. Former prime minister Benazir Bhutto’s son and political heir, Bilawal Bhutto Zardari, will not be appearing in public and a videotape of a recorded speech will instead be played at political rallies. Ms Bhutto was assassinated in a gun and bomb attack in Rawalpindi during the last elections in 2007. “This time the threat is even greater,” said Sharmila Faruqi, a PPP member. “We can’t put the life of our chairman at risk,” she added, referring to the younger Bhutto. The PPP is trying to draw sympathy from an emotional television campaign that relives Ms Bhutto’s final moments.

The Karachi-based MQM says it is facing threats from Taliban elements that have established footholds for themselves deep inside the city.

“The Taliban have strongholds in the Pashtun areas of Sarabkot, Mangophir and Sultanabad,” said Faisal Sabzwari, an MQM candidate whose constituency includes some of the militant-controlled neighbourhoods.Two MQM candidates have been assassinated in recent weeks. On 10 April, Fakhrul Islam, one of the party’s candidates in the southern city of Hyderabad was shot dead. The Taliban claimed responsibility. The next day, another candidate, SM Shiraz, was slain in Karachi.

The secular parties were already faced with a difficult campaign after a strong feeling of anti-incumbency will likely see many members of the outgoing government lose their seats. A poor economy, deep power cuts, and allegations of corruption have eaten away at their support base. Now, they can barely campaign to consolidate whatever loyal support base they may have.

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Rights campaigners have demanded that swift measures be taken to ensure a level playing field. “The time is running out for this to be deemed a free and fair election,” said Ali Dayan Hasan, of Human Rights Watch. “Protection should be given to all parties, particularly the parties threatened, so that they may campaign freely and without fear.”

If the election does go ahead as planned, without hitch, it will be the first time in Pakistan’s history that there will be a peaceful transfer of power from one civilian government to the next.

Election season violence: Major attacks in April

1 April 2013 Bomb targeting ANP party kills two tribal elders in Bannu.

10 April Fakhrul Islam, MQM candidate, shot dead in Hyderabad. Taliban claimed responsibility.

11 April SM Shiraz, MQM candidate, shot dead in Karachi.

15 April Bomb attack on Sanaullah Zehri, PML-N candidate in Khuzdar, Baluchistan, kills four including Zehri’s son, brother and nephew. At least 25 people wounded.

16 April 16 people killed in a suicide bomb attack on an ANP rally in Peshawar. Former minister Ghulam Ahmed Bilou escaped with minor injuries.

21 April House of National Party chief Dr Malik Baloch attacked in Turbat, Baluchistan.

21 April Two ANP activists killed in Pishin, Baluchistan, in attack on election rally.

22 April Grenade attack on ANP office in Swabi leaves two injured.