The referendum was seen as crucial not just for shaping the political system of Turkey but also the future strategic direction of a nation that has been a NATO member since 1952 and an EU hopeful for half a century.
The 'Yes' camp won 51.41 per cent in Sunday's referendum on a new presidential system and 'No' 48.59, according to near-complete results released by the election authorities.
But Erdogan's victory was far narrower than expected, emerging only after several nail-biting hours late Sunday which saw the 'No' result dramatically catch up in the later count.
With the opposition crying foul over alleged violations, all eyes will be on Monday's announcement by international observers from the OSCE and the Council of Europe who will give their initial assessment of the vote.
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"On April 17, we have woken up to a new Turkey," wrote the pro-government Hurriyet columnist Abdulkadir Selvi.
"The 'Yes' was victorious but the people have sent messages to the government and opposition that need to be carefully considered."
The new system is due to come into effect after elections in November 2019.
Erdogan declared that Turkey's had made a "historic" decision and appeared standing on top of a bus in front of thousands of cheering supporters outside his Huber Palace Istanbul residence on the shores of the Bosphorus.
But the opposition were not content to rest on their better-than-expected performance despite a lopsided campaign in which the 'Yes' camp enjoyed vastly greater resources and dominated the airwaves.
Both the main opposition Republican People's Party (CHP) and the pro-Kurdish Peoples' Democratic Party (HDP) said they would appeal the results from most of the ballot boxes due to alleged violations.
"The Higher Election Board has thrown a shadow on the people's decision. They have caused the referendum's legitimacy to be questioned," said CHP chief Kemal Kilicdaroglu.
The HDP said there were indications of a manipulation amounting to three or four percentage points while deputy CHP leader Erdal Aksunger said up to 60 percent of the ballot boxes could be appealed.
Monitors from the OSCE Office for Democratic Institutions and Human Rights (ODIHR) and the Parliamentary Assembly of the Council of Europe (PACE) are to give their own assessment of the vote at 1200 GMT.
"A victory of the nation," said the headline in the pro- government Yeni Safak daily. "Turkey has won."
But the Cumhuriyet opposition daily focused on the alleged violations: "A shadow fell over the ballot boxes," it said.
Throughout the campaign, Erdogan launched bitter attacks on the European Union, accusing member states of behaving like the Third Reich in failing to allow his ministers to campaign among expats.
The initial reaction from Turkey's Western allies was far from ebullient, with top EU officials saying Turkey had to find the "broadest possible" agreement on the changes in view of the closeness of the result.