Parties and groups supporting the Nice Treaty are likely to outspend the No side by at least five to one, according to estimates of how much each side is planning to spend on its campaign.
Groups supporting the Yes side are likely to spend at least €1.25m, compared to around €250,000 for anti-Nice groups.
With just 24 days until polling day, the various campaigns are getting into gear, and posters are going up around the country.
Fianna Fáil says it will spend at least €500,000. The other big spender on the Yes side is IBEC, which also plans to spend around €500,000.
Fine Gael has a campaign budget of €150,000, the Progressive Democrats' budget is €100,000 and Labour has €25,000 to spend.
A number of other pro-Nice groups are unable to say how much they will spend until their fundraising is complete.
On the No side, the biggest budget belongs to the No to Nice campaign, which is planning to raise and spend €100,000.
Sinn Féin will spend around €70,000, the Greens have up to €50,000 and the National Platform has less than €40,000. Other parties and groups will spend far less.
This means that in total, at least €1.25m will be spent promoting a Yes vote, while the No campaign will be lucky to spend €250,000 in total.
The No side was also outspent in the last Referendum. On that occasion, the Referendum Commission spent significant sums publicising both sides of the argument, giving the cases for and against accepting the Treaty.
This time, the Commission is restricted to providing basic information. Some No campaigners argue that this will restrict their ability to get their message across.
Another change from the last Referendum is that groups campaigning on either side are covered by electoral legislation.
This time around, acceptable donations are capped at just over €6,300, foreign donations are banned, and any group that receives a donation worth more than €127 must register with the Standards in Public Office Commission.
