I was shocked by Averil Power's announcement this week. As part of Fianna Fáil since her teens she has always been clear and upfront about her reasons for being a member - and staying a member - of that party. Her own working class background and experience as the first in her family to access third level drew her to Fianna Fáil, the party she credits with championing education and seeking to create an Ireland where everyone has a fair start in life, regardless of how much money they have.
In 2009, when many former up-and-coming Fianna Fáilers ran for the hills and airbrushed their political association from their CVs, Averil fought the local elections for the party, building a strong team and listening - night after night, day after day - on doorsteps as people vented their anger for the destruction wrought on the country, and told their own, personal, tales of woe.
Averil defended the party, her own commitment to it, and its potential to turn around, renew, and again contribute to making Ireland a better place.
In 2011, she was on the doorsteps again, this time for the General Election, hearing the same stories, fighting the same fight. People asked - often - why she was in Fianna Fáil, how she could be in Fianna Fáil after all that had happened. She was firm: she believed in the party, its values and its ability to do good, and, she could deliver more from within than from the sidelines.
As senator, one of just two women, she put up with being front and centre in endless photo shoots in an attempt to provide some substance to the party's claim that it was a modern, balanced party.
But it was the Marriage Equality Referendum that finally did it. The party's unwillingness to get behind such a fundamental issue of equality and rights - and, worse, the old Fianna Fáil style of cute hoorism, keeping quiet, seeing how it would play out, rather than risking the vote locally so near to a general election - was what pushed Averil to jump.
And her exit was dramatic, designed to inflict pain. The aftermath, a party leader launching a very personal attack on a Senator, felt nasty. Averil stood up for what she believed in, fought hard to bring her party around, and ultimately had to admit defeat. Fianna Fáil has no room for such challenges. It didn't like the mirror being held up to its behaviour in the referendum and would prefer to wave goodbye to a lonely senator; rather that than ask the big questions internally. The party assertion that this is about little more than posturing in Dublin Bay North is flimsy, and a blatant attempt to brush over much deeper internal issues.
Averil's exit comes not long after Lucinda's. Another strong, young, committed and determined female politician, who grew up in Fine Gael and wanted to stay there - until she lost the whip.
Lucinda, talking about her new party, Renua, is firm that hers is a party that will invite, and celebrate, critical thinking and challenge. It will not be a party of 'yes men' and women, where people stay quiet for fear of being passed over for promotion. She is vocal in her criticism of "dynastic" political parties for their inability to facilitate anyone who challenges the consensus, for discouraging passion and conviction and for celebrating conformity.
Averil and Lucinda's experiences are similar. Both are conviction politicians, both sought to make their way in large, traditional parties. Both rose through the ranks and had considerable success within those parties, and both exited on a values issue. So what does this say about our parties? Can these large entities nurture and grow politicians of courage and conviction? Can they withstand internal challenges and allow interrogation and push back? Are they willing to take a risk on issues because it is the right thing to do, even if it does cost them votes?
Averil and Lucinda's experience suggest they cannot. These women tried to bring change from within and deemed it impossible.
The real losers here are Fianna Fáil and Fine Gael. Politics is in the business of ideas, and parties - just like companies - are in competition for talent; they need to get it and then they need to keep it.
At a time when female politicians are few and far between and parties are actively seeking them, two of the finest have decided to go it alone. By doing so they send a message to thousands of other women, who may have been looking at those parties as potential homes.
The Marriage Equality Referendum campaign was a turning point in how we collectively discuss the issues that matter to us as citizens. Hundreds of thousands of people took time to engage with the issue, to sift what was relevant from what was not and make a decision about the Ireland they wanted to live in.
In doing that, they recognised and respected those in public life who were prepared to hold strong views and speak openly and honestly about their position.
As former President Mary McAleese said on Saturday, this referendum shifted the tectonic plates in Ireland.
Those plates will now keep moving and the future belongs not to the politics of old, but to people of conviction willing to speak the truth. Averil Power is such a person. She - and others like her - are the future of our politics.