It’s been 45 years since a presidential candidate in the United States has been murdered by an assassin in cold blood, and not since 1864 has the United States held a presidential election in the middle of a war taking place on U.S. soil.

But imagine a national campaign that takes place under constant threat of radical terrorist attack.

That is exactly what’s happening in Pakistan, where a tense campaign has taken place not through the recognizable open-air rallies that mark campaigns throughout the world, but in large part behind closed doors — or at least behind thick glass.

Campaign violence began late in 2012 — members of the pro-U.S., pro-NATO, anti-Taliban Awami National Party (ANP, عوامی نيشنل پارٹی‎ in Urdu, ملي عوامي ګوند‎ in Pashto), the country’s largest Pashtun ethnicity party have long been accustomed to being targets of violence.  But as election day has neared, mainstream parties have been increasingly targeted as well.

The most vulnerable parties have been the incumbent Pakistan People’s Party (PPP, پاکستان پیپلز پارٹی‎) of Pakistan’s president, Asif Ali Zardari, the widower of the late prime minister Benazir Bhutto, who was killed in December 2007 by assassins, and its allies like the Muttahida Quami Movement (MQM, متحدہ قومی موومنٹ), a Karachi-based party.  But even their main rivals, the more conservative Pakistan Muslim League (N) (PML-N, اکستان مسلم لیگ ن) of former prime minister Nawaz Sharif has also been targeted.  The threat of violence is so strong that the PPP has barely held any rallies — it even called off its kickoff rally.  Sharif (pictured above) has campaigned only with extremely cautious protections.

Given that a functioning democracy requires a certain respect for the rule of law and a baseline ability of voters to interact with party leaders and potential prime ministers, the current state in Pakistan is hardly any kind of way to wage a political campaign, and the gruesome toll of violence has led to an eerily subdued campaign season.

The main culprit is the Tehreek-i-Taliban Pakistan (TTP, تحریک طالبان پاکستان), better known simply as the ‘Pakistan Taliban.’

So what exactly is the TTP and why is it trying to destabilize Pakistan’s election this year? 

It’s an umbrella group of around a dozen different groups, most of which are based along the northwestern border between Pakistan and Afghanistan, the Federally Administered Tribal Areas (FATA) that essentially constitute a festering no man’s land from which some of the most radical Islamic groups in the world operate.  United as the TTP for the first time in 2007, it’s a very different entity than the more widely known Taliban in Afghanistan, and it may ultimately be more dangerous.  It’s consistently waged attacks within Pakistan and against the PPP-led government for the past five years and it was behind the 2010 car bomb attempt in New York City’s Times Square.  The TTP is one of the reasons that Waziristan and northwestern Pakistan have become prime targets of U.S. military drone attacks.  The group, which also has ties to al-Qaeda, may have also played a role in the assassination of former PPP prime minister Benazir Bhutto in December 2007.

The country’s army chief of staff, Ashfaq Kayani, who remains a more powerful figure than Pakistan’s prime minister, has ordered extra forces to secure the weekend elections, and nearly 50,000 security personnel will be deployed just in Karachi, Pakistan’s largest city, a particular target, given that it’s the base of the liberal MQM and Sindh province is a stronghold of the PPP.  Already stung by Bhutto’s 2007 death, the PPP has blanched from any large-scale public rallies.

Sharif and the PML-N, with their stronghold in Punjab province to the north, have been spared the worst of the TTP’s campaign, and the TTP itself has said that it will not target the secular, liberal Imran Khan and his Pakistan Tehreek-e-Insaf (Movement for Justice or PTI, پاکستان تحريک) in large part due to Khan’s campaign pledge to shoot down U.S. drones that he argues violate Pakistani sovereignty.

It nonetheless seems certain that the TTP will attempt some violent disruptions on Saturday, which has left Karachi’s residents, above all, in a state of fear:

The talk in Karachi is all of terror, all of bombs and all of fear. One newspaper report details dens of terrorist groups hidden in the industrial zones of the city, another reveals mobile “justice” units that the Tehreek-e-Taliban Pakistan are using to mete out punishments. Shootouts erupt on street corners and large crowds are just invitations to suicide bombers. No one has tears to spare for the three, four, five or seven people killed in targeted shootings day after day.