AT 5.30pm on Wednesday evening, the government backed defence minister Willie O'Dea with its support for a motion of confidence in the veteran Limerick TD. Fine Gael's motion had failed, and under Dáil rules, the party would not be allowed to put down another no-confidence motion in O'Dea for six months. The consensus in Leinster House was that O'Dea was safe.

Just over 24 hours later, O'Dea had resigned from office. As there is no 'smoking gun', the Sunday Tribune has identified the reasons for the transformation of the political landscape. What really made Willie O'Dea jump?

1. Boyle Tweeting Twice

When the government won the confidence vote in the Dáil, the heat seemed to have gone out of the issue. O'Dea looked safe until Green Party chairman Dan Boyle went online and posted his views on Twitter and Facebook. When Boyle tweeted at 6.30pm and 6.35pm, the story got new life and O'Dea's behind was hovering over the bacon slicer.

At 6.30pm, he tweeted, "As regards to Minister O'Dea I don't have confidence in him. His situation is compromised. Probably be a few chapters in this story yet." And five minutes later, he added, "Not happy with what happened today. Believe we bounced into supporting motion (sic). Next week would have been fine."

Replicating a role played by Michael McDowell for the PDs in a previous era, Boyle has developed a national media profile for publicly questioning his own party. He has marched the Greens to the top of the mountain several times only to retreat again. Fianna Fáil is enraged that the senator who has cried 'wolf' so many times before set in motion the sequence of events that led to O'Dea's resignation with a tweet.

2. O'Dea's behaviour in the confidence debate

While the government won the confidence motion on Wednesday, O'Dea's behaviour during the debate that preceded the vote was ill-judged. His aggressive tone and use of his own speech to throw political jibes at the opposition were unwise. Had O'Dea been more contrite and been seen to be genuinely remorseful for his actions with an apology, subsequent events might not have gone against him.

3. The Sean O'Rourke interview

The Willie O'Dea who appeared on RTé radio's News at One on Thursday was an unrecognisable figure compared to the bolshie minister who was so often sent out to bat for the government in media appearances.

Seán O'Rourke opened the interview by putting it to O'Dea: "You really are one hell of a dirty fighter, aren't you?" O'Dea was contrite, downbeat, despondent and sounded like a seasoned politician who knew the game was up. As O'Rourke publicly filleted the minister, O'Dea showed poor judgement in uttering the words: "I'm a victim here as well. Everybody's a victim. I'm being accused of something I didn't do, which is perjury, so from that point of view, I'm a victim." Playing the victim simply did not wash with the public.

4. O'Dea's mention of the Gardaí

Alarm bells rang in government circles when O'Dea turned on the Garda Síochána during his interview with O'Rourke. On Wednesday, Fine Gael's Brian Hayes had made an issue in the Dáil of O'Dea's admission that a garda had told him about the brothel allegations. O'Dea claimed he was given the information during a "casual off the record conversation" with a garda. When O'Rourke asked him if he would co-operate with a garda inquiry and name the garda, O'Dea replied, "I'll cross that bridge when I get to it... How far I'd co-operate I don't know... I'm not saying no." This, coupled with Green member Gary Fitzgerald going to the gardaí, threatened to open up an unthinkable scenario in which a cabinet minister was not fully co-operating with a state inquiry.

5. Frances Fitzgerald's Seanad motion

During the order of business in the Seanad on Thursday morning, Fine Gael senator Eugene Regan, who has to be given credit for making the O'Dea issue his own when nobody else was paying it any attention, raised the matter again. His party colleague, Senator Frances Fitzgerald, made a shrewd political move in putting down a Seanad motion of no confidence in O'Dea. Fianna Fáil's Donie Cassidy claimed there was no precedent for such a move but Fitzgerald had her homework done and recalled a similar motion against Pádraig Flynn in the early 1990s. The motion would have been heard this Wednesday and would have "flushed Dan Boyle out". Could Boyle have voted in favour of O'Dea after his tweet? Would Fitzgerald's move have called Boyle's bluff?

6. The 'Limerick Leader' defence that never came

Green leader John Gormley claims that O'Dea gave him an assurance on Wednesday that an article in the Limerick Leader the following day would clear up the matter and vindicate him. Gormley claims the article did not do that and, in fact, it did "the opposite".

Mike Dwane's article, under the headline 'Willie, me and THAT tape', merely explained how the journalist found himself at the heart of a national controversy and the background to the infamous interview. It was a good narrative account of Dwane's side of the story, from his interview with O'Dea in a Limerick Hotel last March until last week. It did not, as O'Dea hoped, vindicate him.

7. Eamon Ryan's "As I understand it" speech

Taoiseach Brian Cowen, finance minister Brian Lenihan, Labour's Eamon Gilmore and Joan Burton, Sinn Féin's Caoimhghín Ó Caoláin, and Fine Gael's Enda Kenny, Michael Darcy and Brian Hayes all stood up and gave strong speeches for and against O'Dea during the confidence motion debate on Wednesday. The weak link on O'Dea's side of the argument was Green minister Eamon Ryan's "as I understand it" speech, which was poorly prepared and unconvincing. In Ryan's defence, it appears the Greens were completely taken by surprise and "bounced" by Cowen's snap decision to pose the motion of confidence on Wednesday afternoon. Footage of Ryan's performance on news bulletins that night is sure to have set off alarm bells among Greens.

8. The 'Irish Times'

The Irish Times is the daily paper of choice among the Green hierarchy. Paul Gogarty alluded to that fact in his Morning Ireland interview on Thursday morning when he claimed he was surprised at the editorial stance taken by one daily newspaper that morning about the Greens' support of the O'Dea confidence motion. Political journalists Stephen Collins, Miriam Lord and Harry McGee all covered the issue extensively and this clearly worried the Greens.

An article by former Green Party councillor and barrister Vincent P Martin also sent shockwaves through the party hierarchy. His critics might label him an opportunist, as Martin joined the Green party only when it was 'trendy' to do so before the 2007 general election. Others say that he is angling for Déirdre de Búrca's vacant Seanad seat. But Martin's opinion piece on Thursday, and his appearance on Today With Pat Kenny that morning, had an effect.

Martin's article gave a strong explanation as to why O'Dea was fundamentally at fault throughout the episode. More importantly, his piece ended with the killer lines, "The Green Party stands for more. We must be true to ourselves regardless of the consequences. The alternative is to become what we hate." Those lines must have hurt Green sensibilities.

9. The "actuality" of the tape

The transcript of the conversation between O'Dea and Limerick Leader journalist Mike Dwane had been around for some time and its contents had been widely published. But, as commentator Noel Whelan has pointed out, the "actuality" of hearing the tape cannot be played down. Everybody knew O'Dea had falsely linked Sinn Féin councillor Maurice Quinlivan with a Limerick property being used as a brothel. But hearing him say it, and having the tape played over and over again on radio stations from lunchtime on Thursday, was a factor in O'Dea's demise.

10. George Lee

George who? A week is a long time in politics and Fianna Fáil must be wondering where it all went wrong. The question does arise: had Lee not departed, would Enda Kenny have tabled the no-confidence motion? It matters little now. The irony is that the departure of Lee, which damaged Kenny a fortnight ago, may have given him a good week last week.