The "big thing" that has changed is that the Irish economy has suffered a fast, deep and dramatic downturn on an unprecedented scale, said Cox, who is now president of the European Movement, an international organisation open to all political, economic, social and cultural trends in civil society.
"I think there has been a reflection and realisation in the public's opinion that a small economy, in these big economic storms, benefits from being in a safe harbour," said Cox. He said he would personally campaign for the 'yes' camp, during which period he would temporarily step down from his position as European Movement president.
Cox was speaking in Warsaw, where he attended, at the invitation of the Polish authorities, celebrations to mark the fifth anniversary of the 2004 EU enlargement, which saw Poland enter the EU together with seven other Central European states.
Speaking to EurActiv Poland, he described himself as an enlargement "enthusiast". He emphasised the need for the Lisbon Treaty to enter into force before the EU can consider future enlargement beyond Croatia. But he also warned of "commitment fatigue" among applicant countries themselves.
"What I do know, because I still keep an active engagement with the region, especially now with civil society through the European Movement, as commentators speak of enlargement fatigue in Western Europe, there is certainly also a commitment fatigue in some of the countries of the Western Balkans," Cox said.
In the light of the coming EU elections, Cox said it was premature to make assumptions over possible alliances between political groups, where his Liberal group could play an important role.
"For future EU decision-making, it is important to see what kind of stable majorities could be built in order to win qualified majority votes in the Parliament," Cox said.
Asked if he foresaw an alliance between the EPP and the Liberals in the next EU parliament, he did not exclude such a possibility, but stressed that EPP and the Socialists also had a tradition of working together, which he called "business as usual". He said the fact that the two major groups were attacking each other should not prevent them from renewing agreements.
"I should warn against interpreting pre-election rhetoric with post-election strategies," Cox said.
