The AK Party's recent handling of a presidential election has exposed deep divisions over the role of religion in this Muslim but secular state.
Put under pressure by mass public rallies, the army and a court ruling, the government was forced to withdraw its presidential candidate, Foreign Minister Abdullah Gul, an ex-Islamist, and to call early parliamentary polls to avert a full-blown political crisis.
''This will be the most important election we've had for decades.
And it is taking place in a very polarising situation,'' said Suat Kiniklioglu, head of the Ankara-based German Marshall Fund of the United States.
''The AK Party has realised it has not become as accepted or as mainstream as it thought it had. They know they need to make an extra effort now to win over middle-of-the-road voters.'' Prime Minister Tayyip Erdogan's centre-right AK Party has delivered nearly five years of stable one-party government, stellar economic growth, tumbling inflation, surging foreign investment and the start of European Union membership talks.
But Turkey's secular elite, including army generals and top judges, distrust the party's Islamist past and accuse it of wanting to erode the separation of state and religion.
The distrust goes beyond the elite. Millions of middle class Turks joined the rallies in major cities over the past month in favour of secularism and against what they see as the creeping influence of Islam in daily life and the state bureaucracy.
The AK Party springs from a banned Islamist party. Erdogan and other party leaders are pious Muslims whose wives wear the Islamic headscarf. But the AK Party denies any Islamist agenda and says it is a democratic party that reflects the diversity of modern Turkey.
Many middle class urban Turks voted for the party in 2002, because they saw no alternative to the discredited political elite at the time.
The AK Party again needs this vote if it wants to secure another term in office as a single party, opinion polls show.
While some analysts say a coalition government headed by the AK Party could make reforms difficult, others believe such a setup could ease tensions with the secular establishment.
The AK Party's core supporters are religious conservatives in provincial Turkey.
''The AK Party has many devout believers, many liberals too, and people of different religions,'' said AP lawmaker Egemen Bagis, an adviser to Erdogan.
''We want more women representing our party in parliament. We want more people from business. We want to attract people from right and left so we can be more representative of this nation. We are at the centre of the political spectrum,'' Bagis said.
All political parties must submit their lists of candidates for the July 22 poll to the Election Commission in early June.
But some analysts question whether the AK Party really favours more democracy.
''It could be just a facade. The selection of candidates will be done in a centralised, top-down manner, by Erdogan himself. But the other parties are no better in this respect. There is little intra-party democracy,'' said Wolfango Piccoli, a Turkey expert at Eurasia Group, a political risk consultancy.
The AK Party, complacent after years of economic success and no serious political opposition, overplayed its hand in the presidential election, analysts say, believing it could just impose its candidate on parliament.
Ignoring the warning signs from the army and elsewhere, it then reacted to failure by trying to rewrite the constitution and have the president elected by voters instead of by MPs.
The fate of these sweeping constitutional reforms, approved by parliament on a first reading with minimal debate, remains unclear.
Many expect President Ahmet Necdet Sezer -- his own mandate extended by the crisis -- to veto them this week on the grounds they have not been properly thought through or debated.
The AK Party needs to show more humility, some analysts say.
''The AK Party was supported by only one in four voters in the 2002 election, though our system of vote allocation meant they ended up with more than 60 per cent of parliamentary seats,'' said Dogu Ergil, a professor at Ankara University.
''They should heed a little more the views of the three quarters of voters who did not vote for them.'' REUTERS SM SSC1031