It had initially been foreseen that the Treaty of Lisbon would have entered into force by the time of these elections, making them the first to be held under its provisions. However, primarily because of the No vote in the referendum in Ireland, the framework established by the Treaty of Nice will be used again. Amongst other differences, the number of MEPs to be returned depends upon which rules are in effect: while 736 MEPs will be elected under the Nice rules, this number would have increased to 751 if the Lisbon Treaty were in force.