At the ancient, towering gates of Istanbul University, students say, there was once an easy mingling of young women who choose to cover their heads as an expression of their Muslim beliefs, and those who do not.
But now suspicious glances are exchanged and caustic comments murmured under the breath. Students are retreating into their respective secular and religious cliques, emblematic of the polarizing debate in Turkish society over the role of Islam in public life.
"We are uneasy with them, and they are uneasy with us," said Yasemin Saglan, a 24-year-old history student whose flowing black hair was uncovered. "I wasn't against them before, but the scarf has become a political symbol, and I see it as a threat."
The religious-secular divide has been thrown into dramatic relief as Turkey's highest court weighs a case brought against the ruling Justice and Development Party, known by its Turkish initials AKP, which has its roots in political Islam.
The country's chief prosecutor is seeking to dissolve the party and ban dozens of senior officials, including Prime Minister Recep Tayyip Erdogan and President Abdullah Gul, from participating in politics for five years. The prosecutor's 162-page brief alleges that the governing party is a "hub of anti-secular activities," promoting an agenda at odds with the republic's founding principles.
A building crisis
Many commentators describe the court challenge as essentially an attempted coup against a democratically elected government by a secular establishment stung by its defeat in last year's general elections. If the case goes forward, they say, it threatens to erase years of movement toward modernization and greater engagement with the West in a country that stands almost alone in its embrace of both democracy and its Muslim heritage.
The legal struggle is widely regarded as a crisis for Turkey, but one more like a drifting iceberg than a speeding locomotive. Although it could be months before the court makes its ruling, there already are signs of paralysis.
"Until all this, the trajectory for Turkey had been a very positive one," said Ian Lesser, a scholar at the German Marshall Fund in Washington. "But the instability is already hurting the economy, and leaves the way open for more extreme and marginal elements -- nationalists, hard-core Islamists -- to come to the fore."
The prosecutor's case was galvanized by the ruling party's move in February to overturn a ban on women wearing head scarves at universities.
The head scarf has long been a kind of political tripwire for Turks, whose revered founding father, Kemal Ataturk, outlawed Muslim garb in most public institutions. That was one of the cornerstones of Ataturk's vision of a predominantly Muslim but resolutely secular republic.
The governing party in early May filed a court brief in its defense, but Erdogan and his allies may take more aggressive steps to stave off a ruling that many analysts believe will go against the AKP.
One possible maneuver would be for the AKP to seek to amend the constitution to make it harder for prosecutors to ban political parties. But legal scholars say that may be difficult to do while the case is underway.
Although Turkey has a long history of banning political movements deemed subversive, the AKP, despite its Islamist background, apparently believed it would be safe. In July parliamentary elections, the party won 47% of the vote, giving it what leaders described as a decisive mandate to move ahead with economic and social changes begun when it first assumed power in 2002.
One of the party's main aims has been to press ahead with a bid to join the European Union. The EU has already declared that the membership efforts would be deeply compromised if the ruling party were banned.
The Constitutional Court agreed unanimously in March to hear the case, and many analysts believe it is primed to rule against the AKP. The court, which is also weighing the legality of the government's move to end the head scarf ban at universities, has ruled in favor of the secularists in other disputes. The judiciary has traditionally been aligned with the secular camp.
Few regard an amicable resolution as likely. If dissolved, the AKP could rename and reconstitute itself, and quickly return to politics, albeit without some of its most senior leaders. The party also could call early elections, but if results don't change from last summer, the deadlock essentially would remain in place.
Seeking to change the constitution to make it harder to ban parties could be an uphill fight. The government lacks the two-thirds majority in parliament that it would need to do so, and would have to strike an alliance with a nationalist or Kurdish party to prevail.
Erdogan, the country's most popular politician, has already had his share of battles with the secular establishment. A decade ago, he was imprisoned and barred from taking part in politics for reciting a poem that was deemed excessively Islamist.
The AKP, a breakaway movement from a much more stridently Islamist party, campaigned on what it called a "conservative-democratic" agenda that mainly revolves around ensuring Turkey's continuing prosperity. The party's first five years in power saw an unprecedented economic boom.
But after making campaign pledges that it would not try to impose religious values, it quickly raised the head scarf issue, infuriating many people -- particularly in big cities such as Istanbul and the capital, Ankara, where a more freewheeling secular lifestyle prevails. Some women wear skimpy outfits and alcohol is freely available at bars and restaurants.
Going hand-in-hand with the political strife, some analysts say, is a battle that pits the traditional secular elite against a growing class of affluent Turks who are devout.
"I don't see it as a class struggle per se, but it's certainly an issue of people who are much more religiously conservative wanting to challenge how the future of the republic is determined," said Zeyno Baran, director of the Center for Eurasian Policy at the Hudson Institute in Washington.
But the prosperity that helped politically empower more pious Turks is now in peril. The Turkish lira fell and the stock market dropped sharply after the Constitutional Court agreed to take up the case. And the religiously conservative Anatolian heartland, which has became an industrial dynamo, is bracing for fallout from the global economic slowdown.
The nation's biggest business group has warned that the legal battle over the governing party's status will make it very difficult to rebound from that. More worrying to many observers is that the court struggle reflects a growing acceptance of anti-democratic measures to combat a perceived Islamist threat.
"I don't agree with everything the AKP is doing, so I didn't vote for them," said 23-year-old student Serdar Yildiz. "But banning them goes completely against democracy. It's like we're going back to the time of constant military takeovers -- no one wants to see that."