Irish Democrats have signed up hundreds of postal voters in a bid to win the US presidential election for Mr John Kerry.
There are an estimated 40,000 American passport holders in Ireland and all are entitled to send absentee ballots to their states for the November election.
Democrats Abroad Ireland chairwoman Ms Rebecca Woolf said: "We're looking to get more numbers because in the closest states such as New Mexico and Florida, a few hundred votes from us would certainly tip the balance."
In the 2000 election, Mr George W. Bush won the state of Florida by just 537 votes.
Ms Woolf said: "A lot of Americans in Ireland are saying to us 'I didn't vote the last time and look what happened'"
The absentee ballots must be received in the US by October 2nd.
The US citizens who have signed up so far include people who have retired to Ireland, employees of American multi-nationals and the children of Irish-American parents.
"A lot of those people would not consider themselves American but they do have US citizenship. People who were born in the US but who moved back here when they were very young. We've registered a few of those."