The big surprise in the Turkish referendum to make Turkey a presidential system was not that Erdogan's side won, but that it was close enough that opponents are charging fraud based on ballots not being counted properly. It may in fact be that it really did lose by a narrow margin, as some I know said it would. But, officially it won by a bit more than Hillary beat Trump by and a bit less than Brexit won by. What strikes me is how the voting patterns in all of these three resemble each other, even as they differ in many ways on economic, nationalistic, and religious grounds, not to mention broader historical issues.
So the big similarity is that they all seem to have exhibited a pattern of the winning side (not in pop votes in the US) being rural traditional voters in the heartlands of these countries, this not holding in UK where all counties supported the losing Remain side, against urban and higher educated and more secular or minority laden areas. Southwestern Wisconsin switched from Obama to Trump, Northern England came in strong for Brexit, and central Turkey aside from Ankara came in for Erdogan's referendum. Is there a commonality here, global populism?
It may be, but the differences between the countries on the categories of economics, nationalism, and religion are notable. One should not forecast too far into the future about future elections based on this, just to note a more political issue, in the UK the Brexit vote was not obviously authoritarian, with many Brexiteers supporting freedom from supposedly oppressive and undemocratic EU regulators, even if they may have been misled to some degree. In the US, many see Trump as authoritarianb, but some voting for him think he is bringing freedom of some sort, maybe as the Sons of Liberty in Texas fought for the freedom to own slaves. In Turkey this matter is pretty unequivocal, with Erdogan declaring a third round of martial law after imprisoning thousands of innocent people on trumped up charges after the failed Gulenist coup attempt last summer. He is full bore authoritarian, but then he is seeking to replace Ataturk, who was also very authoritarian.
On economics the US and UK look more similar and less like Turkey, although all three have experienced economic problems. In the US and UK, they superficially look good, growing more than many other OECD nations, but they also have very high inequality compared to those other nations, with the outcome that the majority in both nations are not doing better economically. Both have old industrial areas suffering from import competition where an anti-foreigner appeal has a lot of appeal, and did so in crucial states in the US, and portions of England, although not Scotland, where every county voted for Remain. Turkey does not have the extreme inequality or the problem of old industrial areas facing import competition, but after a decade of substantial growth under Erdogan's rule prior to 2012, it has slowed down since and actually had negative per capita income growth in 2015 (have not seen 2016 numbers yet). It is different in Turkey, but the economy is not doing all that well, although this may have fed into the low support for Erdogan's referendum.
I see convergence on nationalism. In all three there has been an appeal to an ethnic core based nationalism, WASPs or whites more generally in the US, English in UK, and traditional Sunni Turks in Turkey. For whatever reason, in all three nations those core groups have responded strongly.,
The matter of religion is more subtle and complicated, but has been dragged into the other two. So in both the US and UK anti-Muslim sentiment has been key, with this easily coinciding with anti-immigrant and foreigner appeals that feed into both the economic and nationalistic arguments. In Turkey it is pro-traditional Sunni Islam that is the key, with the large religious minority Alevis viewed as enemies, along with the ethnic Kurds. The central long term game of Erdogan is to undo the secular Turkish state of Ataturk and replace it with a neo-Ottoman Empire approach, although in the vein of the Young Turks of 1905, with a religious Sultan in charge, even if he does not claim to be Caliph.
Indeed the contradictions on all this for Turkey show up in the matter of Daesh/ISIL where Turkey has gone back and forth, long letting arms and people flow to their areas in Syria to keep the Kurds at bay and dump on Assad. Now they have been cut off from that, and have flipped on their relations with fellow authoritarian Putin in Russia. They seem completely confused, with Trump congratulating Erdogan on his referendum and mostly praising him, even as Trump has sent US troops to back the leftist Kurds fighting Daesh/ISIL in Syria because, hey, they are the only ones willing to go to Raqqa and beat those creeps, just as Obama had figured out some time ago.