A leadership crisis can be a riveting and dramatic event. From Shakespeare to Archer, they have provided fodder for thousands of literary and not so literary works, writes Noel Whelan.
In the modern era they make riveting television, bringing as they do all the components of the best soap operas (and sometimes of the best mafia dramas) into our news bulletins.
Those who enjoy political drama have been spoilt this week with Tony Blair's premiership predictably staggering to an end, and then Mary Harney's surprise announcement that she is set to resign as Tánaiste and Progressive Democrats leader.
The anatomy of a leadership crisis has particular features. An inevitable dynamic emerges and more often than not the incumbent leader falls. Sometimes power seeps away gradually. Other leaders are laid low by disloyalty - political assassination by a thousand cut and runs. On other occasions the demise is quickly precipitated by a single dramatic event.
One thing is certain, however. A leadership crisis, if not carefully managed, can cause enduring damage to a party. The electorate tends to take a dim view of divided parties who self-indulgently absorb themselves in internal affairs for any lengthy period.
It was striking, for example, how before announcing he would resign within the next year Blair felt it necessary to apologise to the electorate for the turmoil which his party exhibited this week.
The Progressive Democrats will need to be conscious of the same risks. While it would be hard to imagine the party doing worse than the polls currently indicate, a drawn out or divisive leadership election can only make matters even more difficult and eat into the limited time available to turn things around before the election.
Harney is retiring as leader after a 13-year term which taken as a whole was extremely successful. For 10 of those years the Progressive Democrats have been in government and she has been Tánaiste. For all that time the party has exerted an influence well above its electoral mandate. Its parliamentary party currently has the largest number of members ever.
Harney may have some time left in the Department of Health if she gets her wish to stay there, but even if not she has already notched up a career of considerable ministerial achievements.
The abolition of smog when she was minister of state in environment was a truly historic achievement. In Enterprise and Employment she also enjoyed considerable success, not least in addressing insurance costs.
Her constituency career has also been impressive. Unlike most of the women who made it to the top echelons of Irish politics before the early 1980s, Mary Harney did not have a father in Leinster house from whom she could inherit a seat.
She did enjoy the wise patronage of Jack Lynch, who nominated her to the Seanad in her early 20s. She went on to develop a new political base in the southwest of Co Dublin, where despite dramatic demographic change, constituencies redraw and her change of party she has held a Dáil seat for a quarter of a century.
It is incorrect, however, to suggest that she is retiring from the leadership of the Progressive Democrats at a high point. On the contrary, her party has seldom been lower in the polls, and at parliamentary party level at least has been deeply divided of late.
Her own approval ratings have halved since she went to the Department of Health. History will judge her work in that department very favourably, but in the short term the public's verdict, annoyed about enduring problems like A&E, has been harsher.
One of the Progressive Democrats' difficulties is that under Harney, as indeed under Des O'Malley before her, the party has never planted deep political roots around the country. It is a niche party geographically as it is in policy terms. Apart from the original O'Malley and Molloy bases in Limerick and Galway, the party does not really exist outside of south Dublin.
There are councillors dotted in places but most of its growth has been by acquisition rather than by organic development. Harney acquired Tom Parlon and his farmers' base in Laois-Offaly, and also persuaded Mae Sexton in Longford and Kate Hayes in Kildare to merge their independent organisations with the Progressive Democrats.
Harney is rightly proud of her achievement in attracting new people to party politics and has high hopes for her most recent signing, Colm O'Gorman in Wexford.
Although a formidable orator, Harney has been less than surefooted as a political strategist - a weakness illustrated by the disastrous 1992 general election campaign, the bizarre decision to sit out the last two European elections and only limited success in local government contests.
Indeed, in the latter part of the Harney years much of the better policy ideas and political attack lines have come from Michael McDowell.
The task facing the next PD leader will not be an easy one. He or she must heal wounds and ensure the party's organisation is ready for the forthcoming electoral challenge and must also set out a positioning that ensures the party is still relevant when that election comes. He or she does not have to be universally liked. The party needs a leader who will fire up the base while also adding a few additional percentage points to its vote share.
The most obvious hunting ground for that additional vote is among that pool of middle-ground, middle-class voters otherwise inclined to vote Fine Gael, or even Fianna Fáil, who share the Progressive Democrat liberal economic outlook and who harbour concerns about Green, Labour or Sinn Féin influence on government.
The Progressive Democrats may yet move towards a consensus around a single candidate. There are many reasons why that would be the wiser course. On the other hand, it looks like New Labour is set to provide us with many entertaining episodes of leadership crisis for months to come.