When Arlene Foster defected to the DUP in January 2004, a very senior and long-serving stalwart of the UUP noted: "Well, Alex, she can kiss her political career goodbye. The DUP only want her as part of a package deal with Jeffrey Donaldson and she'll be left to sit on the back benches, or make tea for Big Ian." Hmm.
Tomorrow, she will make her first conference speech as party leader. Last May, she led the DUP to a stunning victory in the Assembly election, increasing their lead over Sinn Fein from 20,000 votes in 2011 to almost 36,000. Crucially - and very happily from a psychological point of view - she also increased the lead over her old party, from 110,905 to 115,265. And, in the process, brought Mike Nesbitt's hopes of electoral progress to a shuddering halt.
The biggest asset she has in her favour is that she is broadly liked and respected across unionism.
There were some internal concerns when she joined the DUP, but she has won over many of the original doubters and delivered an election victory on a scale that seemed very unlikely just a year ago.
Indeed, a key adviser told me at the start of the campaign that "we would be happy with 35 seats". Instead, they held the 38 they had and came very close in a couple of others.
The party faithful will hail her as a heroine tomorrow. She has the advantage of at least a couple of years until the next electoral test (unless Theresa May opts for an early general election). There is no disgruntled internal cabal briefing against her (although some "old hands" do harbour suspicions about defectors from the UUP holding so much sway in the party). That said, she has big challenges along the way: some of which she should address tomorrow.
Brexit - which the DUP backed, but didn't expect to be on the winning side - has the potential to become a political nightmare for her, particularly in terms of the impact on Northern Ireland's employment and economic prospects.
To a much greater extent than she would be prepared to admit, the Executive's hands will be fairly tightly bound by decisions made elsewhere; and if there is the sort of downturn which some economists predict, then the impact here could be especially severe.
Having supported Brexit, she can hardly turn round and try to blame others if things go badly wrong. More worryingly, it will also put a huge strain on the relationship with Sinn Fein.
So far that relationship has been better than it has ever been. Indeed, Opposition has been the making of their relationship. Having realised that there is now no one else to blame if things go wrong, Foster and Martin McGuinness have reached what has been described as a "non-aggression pact".
They have avoided situations and studios in which their differences could be exposed. They have provided cover for each other. They appointed David Gordon (the former Belfast Telegraph journalist and editor of the Nolan Show) to act as their communications "minder". They jointly put the boot into Mike Nesbitt, Colum Eastwood and Naomi Long.
But the cosiness - albeit orchestrated - of the relationship won't last forever. There are some issues which can't just be fobbed off with a smile and a "we're working together and doing our best" response.
Legacy issues. Cultural issues. Language issues. The blueprint for winding down paramilitarism (which has just had funding halted by the Conservative Government). The transfer process from primary to post-primary. Shared housing. And so on and so on. At some point, the DUP and Sinn Fein will have to make a call on all of those issues.
She will also want to respond to what Colum Eastwood ("the Executive is all guff and no government") and Mike Nesbitt ("she scare-mongered on the doorstep over the danger of Sinn Fein, only to return to Stormont to vote for a Sinn Fein Principal Deputy Speaker, collaborate with Sinn Fein over the appointment of a Justice Minister and collude with Martin McGuinness to use the Royal Prerogative to appoint a spin doctor") said last Saturday.
And she'll want to respond, because she knows that there are many in the DUP who are uncomfortable with the underlying nature of the relationship with Sinn Fein. So, she'll want to portray the Opposition as weak, clueless and divided.
She also needs to address the changing nature of Northern Ireland itself, particularly on social and moral issues. The DUP has changed since 1970. It has changed since 1998. It has changed since 2007. It has changed since she became leader.
It's voting base has deepened and its membership has broadened. It's actually a much more cosmopolitan party than most people imagine. But to remain top dog, the DUP will have to begin to reflect that new, changing Northern Ireland.
Has she, for instance, the courage to permit DUP MLAs a free vote on same-sex marriage, as well as ruling out the use of a petition of concern next time it comes to a vote?
Has she the courage to acknowledge that British citizens in this part of the United Kingdom deserve the same moral and social rights as citizens in every other part of the UK? Has she the courage to admit that a DUP which can reach a political deal with Sinn Fein for the collective good of Northern Ireland is also a DUP which can prove itself tolerant of the views, beliefs and lifestyles of every other citizen in Northern Ireland?
Unlike any other unionist leader in my lifetime - and I'm including David Trimble - she has an opportunity to change Northern Ireland. She has an opportunity to prove that unionism is not a repressive, intolerant philosophy.
She has an opportunity to prove that the lead party of unionism is open to anyone and everyone; where the only criteria for membership, or support, is a belief in the sort of pan-UK unionism which argues that what is legal and permitted in one part of the United Kingdom should be legal and permitted in every part of the United Kingdom.
Arlene Foster is 46. Barring some sort of calamity of politics, or nature, she can probably expect to be leader for a decade.
All leaders have a vision and ambition. Now that she has banked a substantial mandate, tomorrow represents an important moment for her to give both the party and a wider audience a glimpse of that vision and ambition.
She defied expectations by leaving the UUP. She defied expectations by becoming leader of the DUP. I wouldn't be surprised if she continues to defy expectations.
But it will require courage - lots of it.