Pakistan's Supreme Court has ordered the arrest of the prime minister on corruption allegations, raising pressure on a government also facing street protests.
The combination of the arrest order and the protest in Islamabad, led by Muslim cleric Muhammad Tahirul Qadri, raised fears among politicians that the military was working with the judiciary to force out a civilian leader.
"There is no doubt that Qadri's march and the Supreme Court's verdict were masterminded by the military establishment of Pakistan," an aide to Prime Minister Raja Pervez Ashraf said.
"The military can intervene at this moment as the Supreme Court has opened a way for it."
However, the ruling coalition led by the Pakistan Peoples Party has a majority in parliament and lawmakers can simply elect another prime minister if Mr Ashraf is ousted.
In June, Mr Ashraf replaced Prime Minister Yusuf Raza Gilani, who was disqualified by the Supreme Court in a previous showdown between the government and the judiciary.
Elections are due in a few months and President Asif Ali Zardari hopes to lead the first civilian government in Pakistan's 65 years as an independent nation that will complete its full term.
However power struggles will distract the unpopular government from tackling an array of problems - a Taliban insurgency, economic stagnation and growing sectarian tensions triggered by bomb attacks and tit-for-tat shootings.
The military, which sees itself as the guarantor of Pakistan's stability, has long regarded the PPP-led government as corrupt, incompetent and unable to prevent the nuclear-armed country from falling apart.
Pakistan's powerful army has a long history of coups and intervening in politics. But these days, generals seem to have little appetite for a coup. Army chief General Ashfaq Kayani has vowed to keep the military out of politics.
However many believe top military leaders still try to exert behind-the-scenes influence, and any moves by the military in the latest crisis could not happen without a green light from Mr Kayani, arguably the most powerful man in Pakistan.
"Extra-constitutional regime change, or 'outside of the political calendar' if you will, is only possible in Pakistan with the tacit nod of the military, on account of it being a long-time stakeholder in Pakistani politics," said Shamila Chaudhry, an analyst at Eurasia Group.
"The Qadri march was like a trial balloon. The military indirectly sent it out to see if it would work."
Some politicians believe the military will try to dominate the caretaker administration that will oversee the run-up to the polls after parliament is dissolved, which is due to happen in March. An election date has yet to be announced.
The protest by Mr Qadri and his followers has also been seen by commentators as being orchestrated by the military to add to the pressure on Mr Zardari's government, although the military has denied any ties to the cleric.
Thousands of followers of the populist cleric camped near the federal parliament cheered and waved Pakistani flags as television channels broadcast news of the Supreme Court's order to arrest Mr Ashraf on charges of corruption.
Government officials said they were baffled by the arrest order, which came hours after Chief Justice Iftikhar Chaudhry said elections should go ahead as scheduled.