The confrontation between Asif Zardari and Nawaz Sharif may be a crisis too many for Pakistan, writes Graham Usher in Islamabad Pakistan is on the brink. Fighting with the Taliban on the Afghan border, the prospect of war with India is compounded by an economy in freefall. And, a political crisis in this sad, fractured country has erupted between President Asif Zardari, leader of the governing Pakistan People's Party (PPP), and Nawaz Sharif, leader of the Pakistan Muslim League-National (PML-N), the largest opposition party. Violence has flared in Lahore, Rawalpindi, Islamabad and other cities. A sense of collapse is palpable. Collapse had been waiting to happen. On 25 February the Supreme Court barred Sharif and his brother Shahbaz from holding political office. The judgement was made on the basis of convictions from the rule of General Pervez Musharraf, Pakistan's ex- military dictator, who ousted Nawaz Sharif as prime minister in a coup in 1999. Shahbaz was chief minister in Punjab following the PML-N's victory in the province in the February 2008 elections. The Sharifs won't appeal the verdict: they don't recognise the judges because Musharraf appointed them under martial rule in 2007. In any case it's not the judges they hold responsible for the verdict. "It is a political decision given on the directives of Zardari," said Nawaz Sharif on 26 February. "It's a conspiracy to keep me out of politics." Zardari denies he had anything to do with the judgement. It's a measure of his current stock that there's barely a commentator who believes him. The ruling was preceded by weeks of innuendo that the Sharifs were about to be removed. (The US administration was reportedly given advance notice). It was followed by a volley of decrees in which Zardari imposed executive rule from Islamabad and instructed the PPP in the Punjab to form the next provincial government, despite being a minority in the assembly. For many observers the complicity was transparent: Zardari had muscled the Supreme Court so that the PPP could accomplish by fiat what it had failed to do in the elections -- "win" the Punjab, Pakistan's largest, wealthiest and most powerful province. PLM-N cadres were outraged, venting their spleen on state property. But most Pakistanis were dismayed. Less than a year ago the PPP and PML-N had come together in a coalition government not only promising democracy after eight years of military rule; they vowed to end the acrimony that had characterised their civilian governments in the 1990s. The keyword was "reconciliation", invoked as the legacy of the slain PPP leader and Zardari's wife, Benazir Bhutto. It lasted three months. The PML-N wanted the Musharraf-appointed judges removed and replaced by those he had sacked under martial law, above all, Chief Justice Iftikhar Chaudhry. Three times Zardari promised their reinstatement -- and three times he reneged on it. "Political agreements are not hadith or the holy Quran," he said. Publicly the reason given was such an overhaul of the judiciary required a slew of "constitutional amendments". Privately many said Zardari was fearful an independent judiciary would overturn an amnesty on corruption cases he and his wife had brokered with Musharraf on their return to Pakistan in 2007. This is Nawaz Sharif's charge. In May 2008 he resigned PML-N ministers from the cabinet in protest at the chief justice's non-reinstatement. In August the PML-N left the federal government altogether, while maintaining a coalition with the PPP in the Punjab. And in February 2009 Nawaz Sharif said the PML-N would support a lawyers' "long march" to Islamabad on 16 March in one final push to get the chief justice restored. With this the last threads of reconciliation appeared to snap. According to the Sharifs, Zardari then offered them a "business deal": relief in the Supreme Court on condition they stopped agitating for the return of the Chief Justice. The Sharifs refused. PPP spokespeople said the Sharifs' claim was an "absolutely outrageous allegation". But since then Zardari has made no effort to pardon, overturn or delay the Supreme Court verdict, all of which he had the power to do. He may have overplayed his hand. Sources say both Zardari and PPP have been taken aback by the ferocity of the PML-N's response. Not only have PML-N cadres taken to the streets in violent disorder; Nawaz Sharif has adopted a ruthless strategy that aims at severing the PPP from its head. "I don't hold the PPP responsible for this situation. I blame Mr Zardari," he said on 27 February. He has accused Zardari of "plundering millions in Swiss Bank accounts"; called on the Punjab bureaucracy not to obey orders from the central government; and, on 1 March, urged seminary students to join the long march" because Zardari seeks "dictation [from Washington] on each and every internal affair. Do these people qualify to run the country?" Given the visceral anti-Americanism that exists in Pakistan's seminaries this is like tossing fire on gasoline. Is there any way to douse the flames? Sources say Zardari has intimated he might rescind executive rule in the Punjab if the Sharifs dissociate the PML-N from the long march. This is unlikely. Nawaz Sharif has gambled his return to political power on the populist call for the "independence of the judiciary". Few observers believe he will muffle it now. Alternatively, Zardari may use the executive powers he commands to arrest the PML-N, the lawyers and the seminary students before they take the long road to Islamabad. This is of course what Musharraf tried to do with martial law in November 2007, when the superior judiciary was purged and 5,000 lawyers detained. Three months later pro-Musharraf parties were routed in the elections. Seven months later Musharraf was forced to resign. Those who don't learn from history are destined to repeat it -- and never more so than in Pakistan.