Several hundred people gathered in Cairo's Tahrir Square after the rulings to denounce the action and rally against Shafiq, the presidential candidate seen by critics as a symbol of Mubarak's autocratic rule. But with no calls by the Brotherhood or other groups for massive demonstrations, the crowd did not grow.
Activists who engineered Egypt's uprising have long suspected that the generals would try to cling to power, explaining that after 60 years as the nation's single most dominant institution, the military would be reluctant to surrender its authority or leave its economic empire to civilian scrutiny.
Shafiq's rival in the Saturday-Sunday runoff, Mohamed Morsi of the Muslim Brotherhood, said he was unhappy about the rulings but accepted them.
"It is my duty as the future president of Egypt, God willing, to separate between the state's authorities and accept the rulings," the U.S.-trained engineer said in a television interview. Late Thursday, he told a news conference: "Millions will go to the ballot boxes on Saturday and Sunday to say no to the tyrants."
Senior Brotherhood leader and lawmaker Mohammed el-Beltagy was less diplomatic, saying the rulings amounted to a "full-fledged coup."
"This is the Egypt that Shafiq and the military council want and which I will not accept no matter how dear the price is," he wrote on his Facebook page.
Equally blunt was another Brotherhood stalwart, lawmaker Subhi Saleh. "The court, I can say, has handed Egypt to the military council on a golden platter and free of charge too," he said.
In last year's parliamentary elections - Egypt's first democratic ones in generations - the Brotherhood became the biggest party in the legislature, with nearly half the seats, alongside more conservative Islamists who took an additional 20 percent. It is hoping to win the presidency as well.
The rulings, however, take away the Brotherhood's power base in parliament and boost Shafiq at a time when the Islamists are at sharp odds with a wide array of major forces, including the military, the judiciary, and pro-democracy groups behind the uprising.
The court also derailed the broader transition to democracy, rights activist Hossam Bahgat said.
"The military placed all powers in its hands. The entire process has been undermined beyond repair," Bahgat said. "They now have the legislative and the executive powers in their hands and there is a big likelihood that the military-backed candidate [Shafiq] is going to win. It is a soft military coup that unfortunately many people will support out of fear of an Islamist takeover of the state."
On Wednesday, the military-appointed government gave security forces the right to arrest civilians for a range of vague crimes such as disrupting traffic and the economy that would give it a mandate to crack down on protests. Many saw the move as evidence that the generals aim to stay in power beyond the July 1 deadline they announced for handing it over to a civilian president.
All day Thursday, military armored vehicles circulated through Cairo's streets playing patriotic songs as soldiers passed out leaflets urging passers-by to vote in the runoff election. Plastered on the side of their vehicles were posters saying, "The army and the people are one hand."
After the court's decision was announced, an energized Shafiq spoke at a rally that had the trappings of a victory celebration. Backers chanted, "We love you, Mr. President," and the 70-year-old blew kisses to them. In his address, he praised the military and said he hoped for a dramatic change in the makeup of parliament.
"We want a parliament that realistically represents all segments of the Egyptian people and a civil state whose borders and legitimacy are protected by our valiant armed forces," said Shafiq, a longtime friend and self-confessed admirer of Mubarak.