To government critics, the charges seemed to be part of a wide-reaching consolidation of power by Mr. Maliki. Amid the anxiety stirred by the American departure and unrest in neighboring Syria, Mr. Maliki, a Shiite, has tightened his grip on this violent and divided nation by marginalizing, intimidating or arresting his political rivals, many of whom are part of Iraq’s Sunni minority.

Hundreds of people have been swept up over the last two months in arrests aimed at former members of Saddam Hussein’s outlawed Baath Party. In recent weeks, security forces also arrested at least 30 people connected to a former prime minister, Ayad Allawi, a secular Shiite and caustic critic of Mr. Maliki, according to Mr. Allawi’s office. And on Sunday, Mr. Maliki asked Parliament to issue a vote of no confidence in his own deputy, Saleh al-Mutlaq, a Sunni prone to hyperbole who had compared Mr. Maliki to a dictator in an interview.

“Any leading Sunni politician seems now to be a target of this campaign by Maliki,” said Reidar Visser, an expert on Iraqi politics. “It seems that every Sunni Muslim or secularist is in danger of being labeled either a Baathist or a terrorist.”

Mr. Hashimi has not often been described as either. Sometimes abrasive and always self-interested, he was one of the first Sunni leaders to embrace the political process after the American invasion, and lost three siblings to terrorist attacks during the height of the sectarian war.

Image Vice President Tariq al-Hashimi, above, had tried to be conciliatory with Prime Minister Nuri Kamal al-Maliki. Credit... Holly Pickett for The New York Times

“He was someone who tried to be conciliatory with the Shiite Islamists at a time when others did not do so,” Mr. Visser said. “Now, Maliki is going after him.”

An aide to Mr. Hashimi denounced the charges as a witch hunt. “This is a coup over all partners, on political process, on the Constitution,” said the aide, who identified himself only as Abu Aya. “This is the new dictatorship.”