Ben Lowry: Northern Ireland's future in the UK now depends on Alliance voters

I was referring to young people from a Catholic background who, like the star golfer from Holywood, were not much bothered about Irish unity.

No such political trend would be more damaging to the republican project than large-scale acceptance of partition among people who would traditionally have been expected to consider themselves to be Irish.

This is not to say that many such Ulster Catholics were ever likely to become Union Jack flag wavers, but merely that a large minority were perhaps becoming instinctively supportive of the very concept of Northern Ireland and its place in the UK – with all the accompanying baggage such as the BBC as the national broadcaster and voting MPs to Westminster.

One plank of my theory was knocked away yesterday.

Irish nationalism is not slowly declining or withering.

The two main nationalist parties got a whisker under 40% of the overall vote, and overnight the decline of nationalism over a decade was reversed.

The combined nationalist-republican vote had kept falling from 42% in 2007 to 36% last year.

If you add Thursday’s People Before Profit (PBP) vote to the SDLP-SF total it is almost back to 2007 – PBP did not designate as nationalist but it has struggled to win support outside of overwhelmingly nationalist areas.

This all suggests that the position of the Union in Northern Ireland is not quite as secure as it looked a year ago.

If the correlation between Catholicism and Irish nationalism remains similarly high in the decades to come, unionism is in deep trouble given the small but relentless demographic change.

However, another plank of my Rory McIlroy theory is still standing.

One of the most striking things about these results is the success of the Alliance Party, across the board.

Much of the support is in places such as East Belfast, where in a straight fight between a united Unionist candidate and an Alliance one, many thousands of soft unionist Protestants will now opt for Alliance.

But much of the support for Alliance is in areas where it never did well in the past.

The party almost clinched a seat in South Down and reportedly polled well in overwhelmingly nationalist areas such as Downpatrick.

Alliance polled strongly yesterday in North Belfast and it even polled respectably in the most emphatically republican seat in Northern Ireland – West Belfast – where it polled well on the way to 1,000 votes.

Whether Alliance as a party policy is agnostic on the Union is a matter for them.

But how its voters would split in a border poll is now of immense significance.

There are 73,000 of them and they will cast the decisive ballots.

If you add Greens and other unaligned parties, it is around 100,000 voters.

This is a huge number of voters, vastly more than the narrow orange-green margin (the combined unionist vote yesterday was 354,490 while the combined nationalist vote was 334,303).

There needs to be a serious debate within unionism now about a border poll.

The arguments against it are strong – that it will be destabilising.

But there are also arguments in favour that should at least be discussed.

There is a plausible case to be made that it would result in heavy defeat for Irish unity.

Certainly republicans would seize on the notion of a border poll every seven years, as is possible under the current arrangements.

But is there not a case to be made that unionists should perhaps negotiate a single post-Brexit border poll on the understanding that it will be considered to have settled the matter for at least 20 years?