The combination of the arrest order and a mass street protest in the capital Islamabad led by Muslim cleric Muhammad Tahirul Qadri raised fears among politicians the military was working with the judiciary to force out a civilian leader.
"There is no doubt Qadri's march and the court's verdict were masterminded by the military establishment of Pakistan," said Fawad Chaudhry, an aide to the Prime Minister. "The military can intervene at this moment as the Supreme Court has opened a way for it."
Thousands of followers of Mr Qadri camped near the federal parliament cheered as television channels broadcast news of the Supreme Court's order to arrest Mr Ashraf on charges of corruption. He took over in June after judges disqualified his predecessor.
Pakistan's powerful army has a long history of coups and intervening in politics. These days it seems to have little appetite for a coup but many believe it still tries to exert behind-the-scenes influence on politics.
The ruling coalition led by the Pakistan People's Party has weathered a series of crises with the judiciary and military over the last few years and hopes its parliamentary majority will help it survive until elections are called within a few months.
President Asif Ali Zardari hopes to lead the first civilian government that will complete its full term and hold elections. Any move to oust the Prime Minister would not automatically trigger the collapse of his coalition since lawmakers can simply elect another prime minister.
However, power struggles distract the 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 Supreme Court gave authorities 24 hours to arrest Mr Ashraf and 16 others in connection with an alleged corruption scandal involving power plants while he served as water and power minister.
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.
"This was totally unexpected," said an official in Mr Ashraf's office. "The Prime Minister and two or three of his friends were watching Qadri speak on television and this suddenly happened."
Mr Qadri, who played a role in backing a military coup in 1999, returned home from Canada less than a month ago to lead a call for electoral reforms to bar corrupt politicians from office that has made him an instant hit among Pakistanis disillusioned with the state.
In a speech from behind a bullet-proof shield in front of Parliament, Mr Qadri praised the military and the judiciary, the country's two other power centres.