But Brahmi's death, after the unsolved February murder of another secular opposition leader, Chokri Belaid, has stunned Tunisia. "The country is in shock," said Jerry Sorkin, a Philadelphia entrepreneur with long-standing ties in Tunisian business and political circles. "This is not a country like Iraq or Syria, where you have these types of killings."
At a time when the Egyptian military has just ousted a president from the Muslim Brotherhood, and killed scores of his followers, the Tunisian murders raise more questions about the coexistence of secular and Islamist parties. Both murdered men were strong critics of Ennahda, which also has Muslim Brotherhood roots.
Ghannouchi has denounced the killings; the interior minister says they were committed by the same Islamic extremist. But many Tunisians wonder whether they could have been carried out by a radical faction within Ennahda. If not, why hasn't the government tracked down Belaid's killer?
Dissatisfaction with Ennahda has been rising over a lagging economy and delays in writing a constitution. Sorkin, who just returned from Tunisia and travels widely there, says he heard many complaints about the government's closing restaurants and coffee shops in the daytime during Ramadan. This imposition of religious norms, he says, has angered not only seculars but also devout Muslims. "This has cost many jobs," he said, "and I hear religious people say they don't need to be told how to be observant."
Tunisian feminists, who are surprisingly strong for a Muslim country, are also furious at the jailing of Amina Sboui, a young woman who bared her breasts on Facebook as a protest against hard-line Islamism. She sits in prison while political assassins roam free.
The stock of a secularist party called Nidaa Tounes has been rising, and its advocates have been reaching out to rural voters. A recent Pew poll showed that 78 percent of Tunisians are dissatisfied with the direction of the country. Although a majority of Tunisians are observant, Ennahda may be losing voters. The big question is whether the party would accept electoral defeat.
The Brahmi killing, however, raises the more immediate question of whether Ghannouchi can control his followers, or the radical Salafi fringe groups who have attacked a TV station, a cinema, bars, and the U.S. Embassy.
An Egyptian-style coup against Ennahda is unlikely, since Tunisia's army is weak, and the situation hasn't yet reached the fever pitch of secular-religious antagonism in Egypt. But tensions are rising.
The failures of the other revolutions are more painful. The primary test case for Islamist-secular coexistence was the Arab world's most populous country, Egypt. That experiment just ended ignominiously, when the military carried out a coup against the elected president, Mohammed Morsi. Now, instead of fighting it out at the polls, both sides are taking to the streets.
Morsi's chief error was his failure to pursue consensus politics. He frightened moderate Muslim Egyptians with his push to impose conservative Islamic social values and his failure to defend Christians against Islamic extremists.
Still, Morsi's opponents - including the youthful leaders who rallied millions of protesters in 2011 and again last month - have hardly been more democratic. They failed to organize political parties and reach out to rural voters. They also failed to unify behind a single leader, which could have enabled them to beat Morsi at the polls.
Instead, most of these "revolutionary" youths have rallied behind the Egyptian military, which is poised to bring trumped-up charges against Morsi. He and the Brotherhood still command substantial support. Any effort to disenfranchise - and crush - them will lead to constant civil strife.
It is sad to watch young Egyptians embrace generals who may crush them in the future. But it is not surprising. "This is a society that has been ruled by autocrats, in which nondemocratic ideas predominate," said Eric Trager, an expert on Egypt at the Washington Institute for Near East Policy. "How can you have a democracy where there are no democrats?"
Perhaps Egyptians will come to recognize the need for political compromise in the future (a democratic necessity some U.S. politicians seem to have forgotten). Until then, the prospects for Egyptian democracy will remain bleak.
The most hopeful prospect for a successful Arab democracy remains Tunisia, where seculars and Islamists still talk to each other. A hopeful sign would be the swift, credible arrest of the killers of Brahmi and Belaid.
Trudy Rubin can be reached at firstname.lastname@example.org.