No-one could accuse Steve Aiken of holding back as incoming leader of the Ulster Unionist Party.

Before the former submarine commander has even taken office, he has ruled out election pacts with the DUP, a UUP depth charge with potentially profound implications for both parties.

It is a brave move from the UUP leader-to-be, given that at the last General Election only 20% of UUP voters said they were opposed to unionist election pacts - and similarly few DUP supporters were opposed.

It is the most dramatic UUP election rallying call since Mike Nesbitt's "Vote Mike, Get Colum" urgings in 2016, when UUP voters were encouraged to offer lower vote preferences across the divide to the SDLP.

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With Aiken - the third UUP leader in less than four years - the party clearly needs stability and consistency.

And the new boss has clearly decided his party will be liberal, not be DUP-lite. But does no pan-unionism mean a panning for unionists?

The last two General Elections have brought joy and tears to the UUP.

The party regained two seats in 2015, including a notable scalp in South Antrim, as a revival seemed underway. Yet the party sank lower than Aiken's submarines in 2017 when those seats were lost, amid a 6% drop in vote share.

There are two seats where the logic of unionist pacts is obvious.

The last time the UUP contested North Belfast was in 2010, on the ludicrously cumbersome Ulster Conservatives and Unionists New Force (UCUNF) label. The 2,837 votes polled exceeds Nigel Dodds' current 2,081 majority.

That said, Dodds won in 2010 despite the UCUNF candidature and the UUP has weakened since, so the DUP deputy leader may hold on - but he will hardly welcome the UUP back.

In Fermanagh and South Tyrone, the last DUP candidate to stand was one Arlene Foster, in 2005.

Foster's 14,056 votes, combined with 8,869 votes for the UUP's Tom Elliott, offered a clear overall unionist majority, but Sinn Fein's Michelle Gildernew took advantage of the unionist divide, winning with 18,638 votes.

Since then, Gildernew has defended the seat successfully once, lost to Elliott in 2015 and recaptured it in 2017, all in very close contests.

So pan-unionism is no panacea but pacts give unionists a chance.

It is unclear what DUP entry into the fray might achieve but the party might be tempted if the UUP is spoiling its North Belfast pitch.

Aiken takes the view that his re-establishment of the UUP as a "pure" election force is worth the risks.

It may help the party take on the DUP in South Antrim, a UUP gain in 2015 but lost last time.

Beyond the two headline constituencies described above, no pacts may also mean no impacts anyway.

Gavin Robinson's hopes of holding East Belfast from a strong Alliance challenge might be improved marginally by the UUP stepping aside. That happened in 2015 but the UUP was so weak in 2017 that its re-entry into the contest saw the DUP increase its majority.

Further afield, the effects of the UUP taking on Sylvia Hermon are uncertain.

The UUP has not contested the seat since her defection. Logically any movement from her supporters ought to be towards the UUP not the DUP, which is targeting the seat, but logic left politics a while ago.

UUP members will be divided on their leader's no-pacts plan - but like unionist voters, not breaking in favour.

In our party membership survey, only 15% of UUP members said they did not want election pacts with the DUP. 40% said they wanted unionist "electoral alliances or pacts when it suits us" and another 19% said they wanted such link-ups for Westminster elections, more than six times the figure for any other type of election.

Members take the view that Westminster contests are indeed occasions where "it suits us" for pacts.

Yet Aiken is understandably keen for the UUP to be a proud and confident unionist party in its own right, not a plaything of the DUP.

Only one in three UUP voters at the last General Election saw their party as the most effective for unionists.

The new leader wants to move the UUP to where it can capture a pro-Union vote not enamoured with any unionist party.

Part of this movement will be towards a pro-EU stance, given the potential threats to the Union posed by the Prime Minister's form of Brexit.

UUP members and voters are almost evenly split between Remainers and Leavers.

Aiken's party is still significant, holding more than a third of unionist council and Assembly seats.

There is plenty of antipathy within the ranks towards the DUP, for sure.

Only 15% would contemplate a merger with Arlene Foster's party, and 51% say they dislike or strongly dislike the DUP and only half would vote transfer to the DUP in non-Westminster elections.

This compares to 70% of DUP members happy to offer a lower preference to the UUP and 82% of those members wanting unionist electoral pacts.

That one-in-five DUP members are ex-UUP, compared to only 2% of UUP members defecting from the DUP, only increases UUP resentment.

The UUP still likes to see itself as the respectable and selfless face of unionism.

The biggest single criticism of the DUP offered by UUP members is that it is "too self-interested". Far more identified this as the key negative regarding the DUP than seeing Foster's party as "too extreme" or "too religious".

Foster herself scored at 5/10 among UUP voters at the 2017 Westminster election.

So there are potentially serious ramifications for unionist prospects if the new UUP leader avoids pacts.

Aiken is used to charting courses, but this one is simultaneously dangerous and logical.

If it goes awry, unionist MPs will be a minority of Northern Ireland's elected Westminster representatives for the first time ever.

That could unite the UUP and DUP in one thing at least. Mutual recrimination.

Jon Tonge is Professor of Politics at the University of Liverpool and co-author of recent books on the DUP and UUP (Oxford University Press)

Belfast Telegraph