When Tom Elliott became leader of the Ulster Unionists last month, he inherited a party that had once been the dominant political force in Northern Ireland. Indeed, It's the only a few years since the UUP provided the north with a First Minister in David Trimble.

Yet the UUP's slow decline is arguably a process dating back some 50 years, and its eclipse by the DUP now looks definitive.

Past success may underly the UUP's recent problems. Once it was a catch-all party that knit all sections of unionism into a dominant bloc. It still contains a array of competing tendencies, but it no longer retains the power to weld them into a coherent whole.

That problem was underlined by the leadership contest, which highlighted sharp differences over the party's direction. Elliott's remark that he would not attend GAA events or Gay Pride marked him out as the candidate of the traditionalists. The modernisers were represented by Basil McCrea, a somewhat mercurial figure who nevertheless offered a sharp critique of the party's position.

McCrea also highlighted a key dilemma that Elliot will now have to resolve. Under the St Andrews' Agreement, the First Minister will be elected from the largest party in the Northern Ireland Assembly, whether that party is unionist or nationalist. On the basis of recent election results, that is likely to mean a contest between the DUP and Sinn Féin. The DUP presumably agreed to the rule change in the belief that unionists would vote DUP in order to prevent a Sinn Fein victory. Elliot's problem is that his own traditionalist positioning makes it more difficult to counteract that logic.

The danger for the UUP is that alienated modernisers will look towards the centrist Alliance Party, while others continue to drift towards the DUP, who will most likely succeed in holding onto the First Minister's job. In spite of Peter and Iris Robinson's personal problems, the DUP vote held up well across most of Northern Ireland at this year's general election.

The exception of course, was Peter Robinson's own seat of East Belfast, where he was beaten by Alliance's Naomi Long. While it may have been the product of a unique combination of factors, there are aspects of Long's victory that suggest an alternative outcome to the Assembly election, though less likely, is possible.

For one thing, a significant number of voters from the unionist community were prepared to express their dissatisfaction by voting for a non-unionist pro-Agreement party rather than turning to the anti-agreement Traditional Unionist Voice. This marks a fundamental turnaround from the early years following the Good Friday Agreement when grassroots unionist discontent with the Good Friday Agreement was a major threat to its survival.

Several observers have suggested that unionist voters are now sufficiently comfortable with the Agreement, and its guarantee that there will be no united Ireland without a referendum, that they are more interested in other issues.

Indeed one former UUP Minister, Dermot Nesbitt, suggested in an interview with the Belfast News Letter that it was time that the very concept of unionist parties was reconsidered.

He says that unionist parties need to "get rid of the word unionist because the Union is secure".

"They need to make their parties places where others can come and join but not feel they're joining a unionist party.

"But by joining they'd actually be joining mainstream unionism and at the same time we'd embracing national politics and making ourselves part of the Union."

It's just possible that Martin McGuinness could become First Minister if the new mood makes unionist voters less inclined to unite behind the DUP. Appeals to unionist unity to stop Sinn Féin were a notable failure in Fermanagh-South Tyrone at the general election, albeit by the slimmest of margins. 

A number of unionist commentators have said that the election of a Sinn Féin First Minister should be respected, as former UUP press officer Alex Kane noted last month. Kane himself takes a different view:

History isn't just defined by eras, epochs, war and revolution: it is also defined by 'moments' and 'tipping points' – after which things would never, could never, be the same again. I believe that a Sinn Fein first minister – as a consequence of the changes made at St Andrews – would have a hugely damaging impact on the political structures and on the so-called peace process. And it would have that impact precisely because all of the available evidence indicates that Sinn Fein would exploit the title of first minister for purely selfish means.

There's no doubt that there is a powerful symbolism attached to the First Minister's job, but symbolism is all it is. The checks and balances within the Stormont institutions mean that McGuinness would have no more power as First Minister than he currently holds as Deputy.

Given the Republic's economic problems, the prospect of a nationalist First Minister looks less like a stepping stone to an imminent united Ireland than it would have done a few years ago. Yet without that threat, it is not clear what unites political unionism in its present form.