All eyes will be on Ireland today as the Government banks on reversing the electorate's trend of rejecting European treaties at the first time of asking.
Here are some of the key dates in the run-up to vote:
:: January 30: The treaty was agreed by 25 of the 27 EU member states - the UK and the Czech Republic refused to sign up.
:: February 1: A parliamentary body on EU affairs decides to facilitate a national debate on the treaty involving politicians, social partners, academics, economists and ambassadors of EU states. There are 24 sittings.
:: February 28: The Government announces plans for a referendum on advice from Attorney General Maire Whelan. Some Brussels technocrats privately suggest that legally there is no need for a vote.
:: March 2: The treaty is formally signed by the 25 EU states and the process of ratification begins.
:: March 27: The Government announces the date of the referendum and the wording for the proposed amendment to the Irish constitution.
:: March 28: Bailed-out Greece ratifies the treaty with a parliamentary vote - within weeks the country is forced into a snap election.
:: April 13: Bailed-out Portugal also ratifies by parliamentary vote.
:: April 19: Slovenia follows suit and secures ratification in parliament.
:: April 30: The referendum treaty campaign gets under way in earnest in Ireland and among the first warning shots is former minister Eamon O Cuiv, deputy leader of opposition party Fianna Fail, saying he will campaign against the treaty. Within three days party bosses had reined him in.
:: May 10: Taoiseach Enda Kenny refuses to go on a live television treaty debate. An offer by host Vincent Browne to step aside over offensive remarks he made about Mr Kenny in 2010 was also later rejected.
:: May 13: Businessman, anti-Lisbon treaty campaigner, Libertas founder and failed MEP candidate Declan Ganley enters the No camp because the treaty does not deliver a deal on Ireland's bank debt.
:: May 15: French President Francois Hollande is sworn in to the role in Paris after declaring growth policies should have formed part of the EU pact.
:: May 17: Jobs Minister Richard Bruton makes an embarrassing gaffe in a live radio debate suggesting Ireland could vote twice on the treaty. The Government has always insisted this vote is a one-off.
:: May 27: Taoiseach Enda Kenny makes a television address appealing for a Yes vote.
:: May 28: Islanders off Donegal are first to vote with Arranmore experiencing its lowest turnout yet of 43% - a similar pattern across the country could spell doom for the Yes side.
:: May 30: Sinn Fein lose a lawsuit against the independent advice from the Referendum Commission that the Government could not veto the ESM bailout system.
:: May 31: About three million voters take to the polls to cast their vote.
:: July: The target month agreed by the 17 eurozone states to set up the bailout fund under the 700 billion euro European Stability Mechanism (ESM). Once countries representing 90% of the funding requirements ratify the treaty then it gets the green light. Ireland's commitment is 1.592% or more than 1.27 billion euro, rising to 11 billion euro if the entire fund is called upon.
:: January 1 2013: The treaty is in effect with the ESM.