Many ambitions of the UUP evident in the 1998 Belfast Agreement have been realised. The deal received popular endorsement and enshrined the principle of consent. Northern Ireland remains part of the UK for as long as a majority within its confines so choose.
Dublin's territorial claim was removed and British sovereignty recognised. North-South institutions presented no prospect of an all-Ireland government. Violence diminished and an imperfect peace took hold.
Yet, despite taking political risks, the UUP has failed to prosper. Articulating the case that the UUP won the argument may be therapeutic, but is not a vote-gathering exercise.
The DUP ruthlessly exploited fears over prisoner releases, policing changes and Sinn Fein in government, while ultimately acquiescing to most of the Belfast Agreement. The stoutest defenders of their respective ethnic blocs fare best.
The UUP's architect of the Belfast Agreement, David Trimble, argues that his desire for a "pluralist parliament for a pluralist people" was only partly created: "In substance, yes, but the DUP are not actually making the best use of it, because they're still in a mode of feeling that they have to fight Sinn Fein and they have to demonstrate to their voters that they're fighting Sinn Fein. This is part of the reason why the administration is not working smoothly ... The DUP feels that they have to be in competitive mode, rather than cooperative mode."
Trimble has effectively given up on the capacity of local parties to remove sectarian electoral politics, arguing only the presence of UK-wide electoral politics can fulfil this aim. However, the idea does not find favour within the UUP and might further narrow its electoral ground.
The UUP's search continues for a sustained, coherent strategy by which to prise support back from the DUP. A Coleraine focus group member insisted the UUP "need to be streetfighters now. If we're not willing to really take the fight to them (the DUP) now, we'll just slip into obscurity".
This may be correct, but the fight needs a clear basis. A UUP elected representative even claimed that "personal ambition and career" now appeared the main reasons for the existence of two separate unionist parties.
The markers which historically gave the UUP advantages over the DUP have disappeared. The UUP is no longer the party of the comfortable Protestant middle-class, who now either vote DUP, or abstain.
As the DUP stole the UUP's political clothes, the UUP struggled to the point where the DUP's deputy leader, Nigel Dodds, claimed, by 2017, there was "only one meaningful unionist party".
While the UUP has many tireless activists, it also contains many inactive ones. Activism needs to include outreach to those Catholics at least acquiescent regarding Northern Ireland's place in the UK, allowing this may be a shrinking pool, post-Brexit.
Given its historical links to Free Presbyterianism and anti-Catholicism, the DUP cannot appeal to Catholics. Yet, our data shows that the UUP has even less attraction.
The UUP has changed considerably. Its organisation, coherence and discipline has improved, although it still needs refinement, as the mixed messages during election campaigns have indicated.
The integrationist tendencies of the UUP, a party once more comfortable at Westminster (a "Conservative border party", as one elected representative described it) - were revised to devolutionary ones. Yet, this is irrelevant if the UUP is not part of a Northern Ireland government, or Westminster parliament. As the DUP's growth reaped huge rewards at the 2017 Westminster election, the loss of parliamentary seats was acutely painful for the UUP.
The UUP's primary tasks are to articulate a sense of unionist identity and advance a Union unthreatening to those who are not natural unionists. It cannot be a vision based upon appeals to the past, or the defensive insecurities of demographic advantage.
According to the MLA Steve Aiken: "Unionism cannot sell 1950s Britain as the argument for remaining part of the UK ... it appeals to a very small and narrow base ... We have a more outward-looking view (than the DUP). We're not intolerant of others ... We're proud to be unionists. We're proud of the British connection. But, you know, we live on an island with 4.5 million people ... and we need to get on."
The UUP sees its Britishness as rational, contractual and non-sectarian. Severance from the Orange Order allowed the UUP to articulate a civic unionism separated from the Protestantism which is still strong (and often sceptical of such things as inter-marriage) among many members.
But convincing a sceptical unionist electorate that the UUP is the superior custodian of unionist interests is tough. This has been made more difficult by the DUP's change to the Belfast Agreement to ensure that the First Minister is elected by the largest party, a device designed to ensure most unionists vote DUP to prevent a Sinn Fein First Minister.
To combat this, the UUP needs more than hope that the DUP will implode. Even the RHI debacle has, so far, failed to dent the DUP's popularity among unionists.
There is no magic wand - no clear difference between the UUP and DUP - which will revive UUP fortunes. The starkest distinction between the two parties since the Belfast Agreement was Brexit, but the UUP retreated from its pro-EU position after the referendum.
A struggle remains for the UUP leadership to establish a distinct discourse, which will address the wider electorate, while reassuring unionists fearful the rise of Sinn Fein. Many within the UUP feel that unionism lost out after the Belfast Agreement. Most members do not believe the relative peace is permanent, are sceptical of all-island links and wary of nationalists.
The concern for the UUP membership is that, amid the perpetual unionist versus nationalist contest, some would argue there is probably only room for one party on either side of the divide.
A rising nationalist population and the loss of unionism's overall majority of seats in the 2017 Assembly election place the issue of unionist unity - and a border poll - on the agenda. Assuming Sinn Fein continues to eclipse the SDLP, can unionism afford to be divided between two parties?
Intra-unionist rivalry increases the possibility of a Sinn Fein First Minister, a possibility many unionists might still refuse to countenance.
Unionists fear electoral parity between the DUP and UUP could damage both, allowing Sinn Fein to become the largest party. It is easier to vote for the largest unionist party to diminish that risk.
A merger with the DUP would be anathema to most UUP members.
Only 15% support this and UUP leaders have reassured the base that amalgamation with the DUP is not on the agenda. It would hardly be a fusion of equals in the current circumstances - more an absorption of the older party.
There is much enmity and historical baggage. UUP members see their party as selfless and view the DUP as selfish. While there is far more that broadly unites than divides unionists, in defence of the Union, support for Northern Ireland, Protestantism and, to some extent, Orangeism, UUP-DUP relations have often been characterised more by antipathy than empathetic pan-unionism.
The future of the UUP rests on its capacity to win back the confidence of its electorate, offering an inclusive, non-sectarian and fresh unionism which is constitutionally robust - a unionism for all.
It needs clear and cogent unionist messages, a strong leader, some points of distinction from the DUP, an attractive team of potential elected representatives and an activist base using modern campaigning techniques.
It is too soon to write the political obituary of the UUP. It has a deeply loyal membership, prepared to endure lean times, enjoys strong pockets of support and now resembles a proper political party, not the loose conglomeration of feuding groups and autonomous associations it constituted at the beginning of the 21st century.
The rapidity of the rise of the DUP indicates that no party is destined to be in the ascendancy in perpetuity and, given the right set of circumstances and dynamic leadership, the UUP might revive.
The party suffered from the most acute unionist political fracture ever seen, over the Belfast Agreement. Therein lies the paradox for the UUP.
At least partly thanks to the party's efforts and sacrifices, Northern Ireland's future may be more secure; their party rather less so - a case of country before party.