European leaders will be firmly focused on the Republic of Ireland today as it becomes the only country to give people a say on the controversial fiscal treaty.
Some 3.1 million people have the right to vote on whether to accept new rules to dictate strict government spending and future bailout options spearheaded by German Chancellor Angela Merkel.
The major worry in the pro-treaty government camp is that a low turnout could see European reforms rejected by Ireland for the third time in five referendums since 2000.
Taoiseach Enda Kenny will be among the early voters in his home constituency base of Castlebar, Co Mayo in the west of the country.
Polling stations in the 43 constituencies stay open from 7am to 10pm with counting due to begin at 9am on Friday and an early indication of the result expected mid-morning or by lunchtime if there is a close contest.
The Government has repeatedly insisted that, regardless of the result, Ireland will not be asked for its support a second time - a departure from the major Nice and Lisbon treaties of the last decade.
The big talking point as a broadcasting moratorium kicked in at lunchtime yesterday was a last-ditch High Court lawsuit brought by Sinn Fein against the independent advisory body, the Referendum Commission.
The party sought to have the chair Judge Kevin Feeney retract remarks that Ireland would not have recourse to the proposed European Stability Mechanism (ESM) bailout fund unless the treaty was backed.
Sinn Fein lost but faced a barrage of attacks from government ministers, including the deputy prime minister, Tanaiste Eamon Gilmore, who accused them of desperate scaremongering and a publicity stunt.
Three recent opinion polls have revealed a 60/40 split in favour of the European fiscal treaty among Irish voters but the No side are always boosted by lower voter turnout and whether the middle class vote can be mobilised is likely to determine the outcome.
The Taoiseach has said he is confident, but never over-confident, before polling day but his number two refused to make a call.
"We are going to continue working right up to the end of polling tomorrow evening, asking every Irish citizen to vote Yes," Mr Gilmore said.
His Labour Party colleague, Minister for Social Protection Joan Burton, claimed victory for the Yes side.
Ireland is the only country in Europe holding a referendum on the treaty as it is obliged to put major EU reforms to the public test, according to the Constitution.
Its record is unpredictable, having rejected the last two at the first vote only to accept the EU reforms in a re-run the following years. Regardless, the treaty will come into effect with the support of 12 states, with or without Irish support.
Voting has already taken place in some islands off the coast of Ireland - in Donegal voters cast ballots on Monday on Tory, Gola, Inishfree, Inishbofin and on Arranmore which, with 43 voters from an electorate of 173, had its lowest turnout ever.
The Mayo islanders polled on Tuesday while the Aran islanders and others off Connemara voted yesterday and the seven islands off the south-west of Co Cork vote with the rest of the country today.
A total 25 of the 27 European Union states have accepted the text of the treaty - with the exception of the UK and Czech Republic.
Only three states have ratified the treaty in full - Greece, Portugal and Slovenia - while six others have begun the process including Germany, Poland, Latvia, Romania, Austria and Denmark.
Despite initial support, the deal has encountered some obstacles following a number of political shake-ups across Europe.
Newly-elected French President Francois Hollande took a different stance from his pro-treaty predecessor Nicolas Sarkozy and warned his government would not ratify the deal unless amendments are included on growth.
Details of a new stimulus plan that is to be stitched into the treaty are expected to be formally considered at the next Euro summit in June.
Chancellor Merkel was forced to postpone her country's ratification of the deal after she was unable to get majority support in the Bundestag.
If passed, the treaty will see stricter budgetary rules imposed on member states and penalties for those that fail to meet them.
The objective of the treaty is also to keep a control on deficits and ensure greater checks and balances are in place for money in and out of each country.
The Yes camp, including the Fine Gael, Labour and Fianna Fail parties, has argued that ratification will ensure Ireland has access to emergency funds from Europe should it require a second bailout.