Campaigning for Turkey's constitutional referendum has not officially started, but the campaign over whether to grant President Recep Tayyip Erdogan sweeping powers is already in full swing on social media, highlighting deep polarization within the country. 

Erdogan's supporters argue that the country needs a strong leader after last July's failed coup attempt and a string of terror attacks, and with its shaky economy. Opponents say the changes will further strengthen an authoritarian leader and turn Turkey into a dictatorship.

Erdogan must first sign the constitutional amendments passed by parliament on January 21 after a short debate marked by brawls between lawmakers. His likely signature will trigger official campaigning for a referendum in April that could dramatically change the country from a parliamentary system to one that concentrates power in the presidency.

In Erdogan's Turkey, media are under assault and dominated by pro-government outlets that are ramping up support for the vote and crowding out or ignoring the voice of opponents. The dearth of information about what the constitutional amendments mean and the pro-government slant in coverage has raised concerns over legitimacy. Adding to worries about the openness of debate, the vote is set to take place under a state of emergency.

Ahead of official campaigning, a series of videos posted online by celebrities, sports stars and others supporting an "Evet," or "Yes," vote has sparked a heated debate on social media. They have in turn been countered by a "Hayir," or "No," campaign, a significant development in an information environment dominated by pro-government mouthpieces.

The social media battle was started by the television commentator and former footballer Ridvan Dilmen, who posted a video online voicing his support for the presidential system.

"Our homeland, our country is passing through a very tough period. A real war of independence. We want a strong Turkey. For a strong Turkey, yes, I am in," said Dilmen.

Dilmen's support triggered a chain reaction of videos supporting the presidential system. Similar to the Manikin Challenge or Ice Bucket Challenge, a person is challenged by someone, who in turn challenges someone else to throw in support.

"Coach Ridvan, I got your call. I'm in for a strong Turkey too," said footballer Arda Turan, who plays for Barcelona.

A number of musicians, actors and other celebrities have since voiced their support in videos. So, too, have Sports Minister Akif Kilic, Foreign Minister Mevlut Cavusoglu, Energy Minister Berat Albayrak - Erdogan's son-in-law - and Prime Minister Binali Yildirim.

But the call to support a "strong Turkey" has, if anything, underscored the country's deep polarization. It has also brought out opposition voices to challenge the government's stance on an open platform. 

Dilmen and Turan have come under heated criticism from football fans on social media, especially from the left. On Friday, at least two dozen mostly leftist football fan clubs, including supporters of Fenerbahce, Galatsaray and Besiktas, started a Twitter campaign against the referendum and called on other clubs to join.

Sol Acik, a leftist Fenerbahce fan group, carried pictures of Dilmen, a former Fenerbahce footballer, that implied their support for him had died. "We commemorate with deep sorrow and regret the death of Ridvan Dilmen 1962-2017," they wrote on Twitter.

The "Hayir" camp has also drawn the support sports stars, musicians and celebrities. But those against the presidential system are regularly labeled traitors or terrorists by Erdogan's supporters.

Some of the "Hayir" videos are quite creative, unlike those from the pro-government camp, which generally simply state support for a "strong Turkey" in videos under 30 seconds.

"Those that have supported the presidential system in videos have no creativity, they just look into the camera and say 'Yes,' that's it," said Ilker Kahlo, who made a popular "No" video. "It is not a challenge to declare support for those in power."

The risks for those against the presidential system are higher than for those towing the government line. A mob attacked the headquarters of the public employees union in Ankara this week after its president argued against the presidential system.

Thousands of people in Turkey have been harassed or investigated for social media posts. In the past, authorities have throttled the internet and blocked social media - going so far as to call for banning Twitter and creating a domestic version. Ironic, then, that it is now being used to support Erdogan's dreams of an empowered presidency.

If approved in a referendum, the constitutional changes would give Erdogan the power to dismiss ministers and parliament, issue decrees, declare emergency rule and appoint figures to key positions, including within the judiciary. The changes would also allow Erdogan to rejoin the Justice and Development Party (AKP), which he helped co-found but was forced to severe ties with when he became president.

Polls on support for the constitutional changes are uncertain, but Erdogan and the AKP will have all the power of the party and state to organize around securing its passage. Whether the referendum passes may come down to how many supporters of the ultranationalist National Movement Party (MHP) throw their support behind the new system.

The AKP was able to get the support of some MHP lawmakers in parliament to pass the constitutional changes, but the party is deeply divided. The main opposition center-left Peoples' Republican Party (CHP) and pro-Kurdish Peoples' Democratic Party (HDP) oppose the referendum.