Fair question.
The AK Party is basically the Turkish version of the Muslim Brotherhood - they represent what you can call populist Islamism. The Brotherhood and like-minded groups have never emphasized implementing the shari'ah as a priority of their political programs. They were founded and are typically run by laymen - professionals, administrators, etc. - not Muslim 'ulama. The emphasis of the Brotherhood has always been on seizing control of and consolidating power in the state, in advance of any program to implement the shari'a. In other words they envision a top-down Islamization, but they need to hold the reins of power in the state before anything else. The reason for this is due to their experience of repression at the hands of secular forces (the Turkish military, Nasser's regime in Egypt, the Tunisian regime, etc.) which led them to (wisely IMO) conclude that these societies weren't ready for a full-scale implementation of the shari'a yet, and any attempt to do so would inevitably alienate the most powerful factions in society. This is especially true in countries like Turkey and Tunisia, where secular ideology and institutions have been so firmly entrenched - but even Hamas, almost a decade into its rule of the Gaza Strip, has refused to fully implement the shari'a, seeing their rule as not fully consolidated (and probably waiting for the day they believe they'll capture the rest of Palestine). So the AK Party's Islamist orientation just isn't visible in society the way many might expect (i.e. as you would see in Saudi Arabia and Iran). The Brotherhood and its related groups are playing a much longer, cautious and more subtle game, best expressed, ironically, by this quote from Erdogan's arch-rival Fethullah Gulen:
"The existing system is still in power. Our friends who have positions in legislative and administrative bodies should learn its details and be vigilant all the time so that they can transform it and be more fruitful on behalf of Islam in order to carry out a nationwide restoration. However, they should wait until the conditions become more favorable. In other words, they should not come out too early."
On the other hand, these movements typically express their Islamist orientation through pan-Islamic solidarity in international affairs, which is what has driven Erdogan's popularity among many Muslims across the world, but which also leads him to make stupid statements like "Muslims are incapable of committing genocide". At a time when many Muslims feel on the defensive, it's natural for them to gravitate towards powerful leaders willing to step up on the world stage and defy convention. But it shouldn't blind them to the realities of the nature of these movements' ultimate goals which are, IMO, totalitarian.
