By ruling out coalition with Fianna Fail and throwing in his lot with Fine Gael, Rabbitte has shown he doesn't lack the bottle to succeed in politics.

But he is certainly playing a high-stakes game and, given the huge gap Fine Gael and Labour have to make up on Fianna Fail, he must be acutely aware that the deck is stacked against him.

That is why it is so tempting to believe that Rabbitte's controversial call for a reassessment of the country's immigration rules is less about the Irish Ferries' dispute and more about pure politics.

Comparisons in some quarters with Enoch Powell or Oswald Mosley are quite clearly ludicrous, but there can be no denying how dramatic a shift in position Rabbitte's comments represent for a Labour Party that likes to portray itself as the conscience of the nation.

There was a particular irony that Rabbitte made his comments in, all of places, the Irish Times. One of the criticisms of the party over the years has been its perceived obsession with how its actions and policies will be judged by the paper of record.

Fianna Fail is by no means above obsessing about the media. But equally, given a choice between the endorsement of the chattering classes or the backing of the ordinary man on the street, there is no doubt where Fianna Fail's priorities lie. The suspicion in the past is that Labour has rarely shown that level of political pragmatism and toughness.

Until now. Rabbitte is a politician to his very fingertips and good politicians know that ideology matters little in Irish politics. Who, other than a tiny minority, pays any attention or cares as to whether a party is left of centre or right of centre?

The belief is that when Michael McDowell brought forward the citizenship referendum in 2004, Rabbitte's instincts leaned towards backing the proposal but that the party's national executive ensured that Labour would oppose it.

Labour may have received kudos among liberal-minded commentators for its stand, but it will not have escaped Rabbitte's notice that the measure was passed with a thumping 4-1 majority.

Being on the side of angels is no guarantee of electoral success.

Eighteen months on, Rabbitte is clearly in a much more commanding position, having won the day at the party conference last year for his strategy of alliance with Fine Gael. There are many Rabbitte-sceptics in the Labour Party and the leader will only have one chance at getting into government, but until that election, he is now very much calling the shots.

Traditional Labour activists must have viewed with disquiet . . . and a sense of helplessness . . . Rabbitte's comments on immigration.

The move has fuelled suspicions inside the party, and beyond, that the leader is cynically responding to focus-group research . . .

something which strategists in other parties say Labour has been bad at doing over the years.

With long-term unemployment down at just over 1%, there are serious credibility issues surrounding Rabbitte's claims that displacement is a major problem. And given that Poland and other eastern European countries are now in the EU, it is difficult to know what, in practical terms, can be done to limit the number of workers from such countries coming here, even if the economy did not need tens of thousands of immigrants to cater for labour shortages.

But in pure political terms, it is hard to see much downside from Rabbitte's comments. Some observers believe that by moving his party to the right, the Dublin South-West TD runs the risk of losing liberal voters . . .

traditionally attracted by Labour's politically correct message . . . to the Greens in middle-class areas or Sinn Fein in working-class constituencies. Maybe, but one has to assume that if Rabbitte is coming out and saying that there is no need to increase taxation or that perhaps a permits scheme ought to be implemented for non-national workers, then he is doing it for sound political reasons, backed up by focus-group research.

It was also interesting to see Rabbitte popping up on the pages of the Irish Sun last week with a guest column questioning the merits of the appointment of Steve Staunton and Bobby Robson as managers of the Irish football team. It is the kind of populist stuff that has become Bertie Ahern's trademark and is a million miles from the Labour party of Ruairi Quinn or Dick Spring.

But if Rabbitte is going to achieve his goal of driving Fianna Fail from office and teaming up with Fine Gael and the Greens in government, then he simply cannot afford to depend on the party's core middle-class vote.

The Rainbow parties need to win an additional 24 seats if they are to take power and, even with all the progress that Fine Gael has made under Enda Kenny, that is a massive ask.

While Fianna Fail is certain to lose a clatter of seats, Ahern remains a very warm favourite to be Taoiseach after the next election.

Those in Labour who opposed Rabbitte's pact with Fine Gael will be pointing out that if their leader had not ruled out going into government with Fianna Fail, everything right now would be pointing to an FFLabour alliance post-2007.

Rabbitte made the call from the outset of his leadership that Labour could not afford to keep its options open, as it attempted to do in 2002. He believes that by failing to present an alternative to Fianna Fail and the PDs in the election, the result was handed on a plate to the government. Labour attempted to ride two horses in the run-up to the last general election and ended up being unseated from both. Rabbitte was determined to ensure that didn't happen again.

It was, and is, a brave gamble. Nobody in the party . . . even his critics . . . doubt that Rabbitte is anything other than genuine and sincere in his views on this matter, but there are those who wonder whether it is the right strategy for the Labour party.

Only the general election will reveal if those who believe that Rabbitte has closed off the most likely avenue for Labour's return to government, and provided a fillip to Fine Gael at the party's expense, are correct.

But for Rabbitte there is no going back. The Rainbow offers his sole chance of a pot of gold. The political reality is that populism, not the party's liberal conscience, is what's required if Rabbitte is to defy the odds and help unseat Bertie Ahern. Those who fret over the soul of the Labour Party may not be impressed, but Rabbitte has proved that he possesses the necessary political ruthlessness to take on Fianna Fail.