People both for and against a stronger European Union stepped up campaigning Wednesday before a national referendum that could determine the fate of the EU's charter for reform.

But many voters said they were still confused by the issue.

As many as 2.8 million Irish citizens will vote Thursday to determine whether Ireland will ratify the European Union's so-called Lisbon Treaty. The treaty, which would streamline decision-making in the 27-nation EU, is meant to replace a draft constitution that was rejected by French and Dutch voters in 2005 and then abandoned.

If the new treaty is adopted by all European Union members, it would create the positions of EU president and foreign policy chief, and reduce national veto powers.

Supporters are optimistic that, if Irish voters approve it, the treaty can be ratified by all members this year because no other EU country is putting it to a referendum.

But some voters are not too sure about it.

"All I know is that nobody understands it," said one voter, Patricia Quigley, 28. "Nobody has a clue ... maybe one or two."

Educational booklets about the ballot were sent by an independent group to more than 2 million households. The campaign also included advertisements in newspapers and on billboards, radio, television and public transportation. Younger voters were targeted on social networking sites such as Facebook and Bebo.

"The 'yes' vote would probably be the most popular, but a lot of people still don't understand it," said Margaret O'Toole, 55, who manages a cafe in Dublin that counts celebrities such as U2's Bono as customers. 'I think a lot of people aren't going to vote because they don't know.'

Three opinion polls in the past week have found support for the treaty anywhere from 7 percentage points ahead of the "no" vote" to 5 points behind.

The Lisbon Treaty would trim the European Commission, the EU's executive body from 27 to 18 members; increase decision-making based on majority rather than on unanimous votes among nations; and increase the policy-making powers, but prune the membership, of the European Parliament.

Most of the Irish establishment -- the government and opposition parties, employers, major newspapers and the Irish Congress of Trade Unions -- support the treaty as the best possible deal for Ireland. They argue that an Irish "no" would undermine the nation's diplomatic clout and its attractiveness as a base for foreign companies.