In a largely Muslim country that sits at the crossroads of East and West, Turks who treasure secular rule are again warning about a “creeping coup” of political Islam.

The cause this time? Constitutional amendments pushed by the elected government, run by Prime Minister Recep Tayyip Erdogan and his party, the Islamic Justice and Development Party (AKP).

Turks will vote on the amendments Sept. 12 in a referendum. Most of the changes are not very controversial but secularists are alarmed over one that gives the president and parliament more say in appointing senior judges. Currently, senior judges vet their own judicial candidates – an inbred system.

Critics say giving the government a greater role in appointments undermines the independence of a judiciary that has staunchly defended the strict separation of mosque and state – and gone head-to-head with the religiously minded government.

But Prime Minister Erdogan maintains that this change, and all the amendments, are another step on the path to Turkish democracy. Indeed, they meet criteria for Turkey to join the European Union.

The clash over Sunday’s referendum should signal to Erdogan the ongoing need to build trust among the broader population as he boosts the brightness of this rising star over Europe and Asia.

The AKP has been in power since 2002, a period of strong economic growth and relative stability that won the party backing again in the election of 2007. The devout Muslim prime minister has ambitions for his country of nearly 80 million people. He sees it as an important player in energy and as a regional problem solver.

Along the way Erdogan has also mixed the Islamic religion with politics, attempting to criminalize adultery, for instance, and trying to lift the ban on women wearing the head scarf at universities – both of which failed. Since the 1970s, Turkey’s high court has shut down four Islamic political parties. Erdogan himself was jailed, and he refashioned himself and the AKP along the lines – he says – of Europe’s Christian Democrats.

But Erdogan’s pushing of the Islamic agenda unnerved secularists, who fear a secret agenda of full Islamization. They’ve watched warily as the AKP government has drawn closer to Iran, Syria, and Iraq and left longtime ally Israel in the diplomatic dust.

Critics worry also about an increasingly autocratic government, pointing to sweeping arrests related to a supposed coup conspiracy. The media have been cowed or bought by the AKP, and official wiretapping abounds. The populist Erdogan often sounds dogmatic and threatening. When he warned a business group that it faced “elimination” if it opposed the referendum, the European Commission sternly rebuked him.

In truth, the constitutional changes conform to democratic norms. They strengthen individual rights, privacy, and unions. They bring the military – which ousted four governments in the last 50 years – further under civilian control.

But the abstract truth is not the same as the political reality in Turkey. The reality is that this is a polarized country, with a large segment of the population increasingly mistrusting of the government.

The vote on Sunday is expected to be close. How close should give Erdogan a good idea of how much trust-building he needs to do ahead of elections next year.