Turkish citizens will head to the polls on Sunday to vote on a new draft constitution which could dramatically increase the powers of President Recep Tayyip Erdogan.
The fast-approaching referendum could prove to be the most controversial political change in a generation with potentially far-reaching and longstanding consequences.
CNBC takes a look at everything you need to know ahead of the vote.
What is the referendum about?
Voters are being asked to decide whether to shift Turkey from a parliamentary to a presidential republic.
A Yes vote would institutionalize a de facto one-man rule with Turkey's powerful yet divisive premier at the helm while a No vote would reject Erdogan's enduring wish for drastic reform.
Turkey's president has argued the reforms would streamline policy implementation and bypass the unnecessarily arduous parliamentary processes that have historically restricted progress.
Whereas, a No vote would reject the chance for Turkey to become a presidential republic and block Erdogan's attempt to wield greater powers.
Why does it matter?
"This vote represents a radical transformation that consolidates the power to a centrally executive president rather than a parliamentary system… that's why it matters," Fadi Hakura, an associated fellow and manager of the Turkey Project at Chatham House, told CNBC in a phone interview.
"If it's a Yes vote, it will codify the vast influence in Turkish politics and Erdogan's already vast influence in policy making. If No, it will shake and undermine the prestige and dent the aura of invincibility that has so far defined his tenure in politics," Hakura added.
Will a Yes or No vote triumph?
"Erdogan knows it's on a knife-edge…" Michael Taylor, senior analyst at Oxford Analytica, told CNBC in a phone interview.
"The Dutch and German developments really benefitted Erdogan… I mean he is a terrific campaigner, he engages with the people and his finger is really on the pulse, so I suppose he is a good populist in that sense," Taylor added.
Erdogan's international campaign for a Yes vote has received widespread disdain. Turkey's leader embraced a bitter row with his European neighbors and even described Dutch and German authorities as behaving like Nazis.
Erdogan has resolutely campaigned for Turkish citizens living abroad to back him in the vote and so the Netherlands and Germany's decision to bar Turkish officials from attempting to rally support in their respective countries sparked fierce criticism from Turkey's president.
Two Turkish opinion polls published Wednesday showed a slim majority for the Yes campaign with around 51 to 52 percent of citizens saying they would vote in favor of the constitutional reforms proposed, according to a Reuters report.
"I think Erdogan will score a narrow victory, similar to Brexit," Chatham's Hakura predicted.
What are the ramifications of a Yes vote?
"A yes vote could be a way to gradually and eventually de-escalate some of the geo-political tensions Turkey faces currently. The big takeaway is that there is this sense now that it's the optimal condition for a referendum for a new political system," James Sawyer, researcher at Eurasia Group, told CNBC in a phone interview.
Erdogan's critics have decried his bid for enhanced powers and pointed to his presiding over a country which is the world's biggest jailer of journalists and a country which has arrested or suspended over 140,000 people since the failed coup attempt in 2016.
"Erdogan is clearly the wrong sort of person you would want to have untrammeled power," Taylor told CNBC.
"Around 85 percent of Turkey's revenues go to central government… so just imagine the centralized power of a President in this case," Hakura said.
And if Erdogan loses?
"It would be a terrific slap in the face to be rejected… he would likely take it very personally. Then again, if it is a No vote, he could well carry on acting as president anyway," Taylor said.
"If it is a No vote then things will become more difficult, the ways to achieve executive powers later will likely become more divisive," Sawyer told CNBC.
What happens next?
"I expect that the consequences from this vote will be felt in the medium or long term, nothing is going to change the very next day," Sawyer said.
Turkey's political fate hangs in the balance with just days to go until Sunday's referendum though Teneo Intelligence analysts suggested whatever the outcome, the country's economic trajectory remains negative for the foreseeable future.
"The amount of damage already inflicted to Turkey's social fabric, institutions, rule of law and business environment is significant. A pervading climate of fear and siege mentality are now deeply instilled in Turkish society and mounting concerns about vote rigging could deepen polarization and grievances… A 'normalization' of Turkey's domestic politics is unlikely to occur regardless of the result," Teneo analysts said in a note.
