The pressure is on Arlene Foster to step aside after Sinn Fein's advance

The next question is which party – the DUP or Sinn Fein – has most to fear from the reimposition of direct rule from Westminster?

DUP leader Arlene Foster arrives to cast her vote at a polling station in Brookeborough (AP)

The fall in the Democratic Unionist Party’s share of the vote increases the pressure on its leader, Arlene Foster, to step down. It doesn’t change the arithmetic of the Northern Ireland Assembly, but it changes the psychology. The DUP still has – just – more first-preference votes than Sinn Fein, and will probably still have more seats when the counting is finished tomorrow.

That would mean there would be no change in the mechanics of making a new executive, which requires the DUP to nominate a first minister and Sinn Fein a deputy to form a joint leadership. But the reduction in the DUP’s share of the vote – and the big rise in the Sinn Fein share – puts Foster further on the defensive, and gives Sinn Fein no incentive to do a deal with her. On the contrary, Michelle O’Neill, the Sinn Fein leader, has more of an interest now in waiting to see if the DUP will now decide that Foster has had her chance and replace her – at least temporarily while the “ash for cash” investigation is completed.

And that depends largely on which party has most to fear from the reimposition of direct rule from Westminster, which is what will happen if the parties fail to reach agreement within three weeks. The last time an agreement was forged, 10 years ago, in the deal that put Ian Paisley and Martin McGuinness in power, they were pushed together by the threat of – of all things – water metering, which Peter Hain, the Northern Ireland Secretary wanted to impose. Can James Brokenshire, Hain’s successor, come up with something so mundane and so persuasive to bring the parties back together as the threat of higher sewerage charges?

This was an election caused by an equally unlikely issue, a badly designed subsidy for green energy. It predictably led to farmers heating empty sheds to claim large sums of public money, while Foster was Minister for the Environment. Sinn Fein has exploited Foster’s embarrassment ruthlessly, and its tactics have been vindicated at the polls. Foster, on the other hand, ran a poor campaign, trying unsuccessfully to focus on Gerry Adams.

Sinn Fein will be riding high on these election results. On a sharply increased turnout, the party has won back the vote share it lost 10 months ago and more, to take its highest share of first-preference votes ever, nearly 28 per cent. The non-sectarian Alliance Party gained vote share too, to a record 9 per cent, with the DUP, minor parties and independents losing ground.

And Sinn Fein would probably gain more from the reimposition of direct rule than the DUP in the propaganda war: it could be presented as a step backwards from greater Irish unity and cooperation. Together with Brexit, which 53 per cent of Northern Irish voters voted against, and which is likely to “harden” the border with the Republic, direct rule would energise Sinn Fein’s supporters even more.

Against such sentiment, Brokenshire will be hard pressed to find compelling practical incentive for the leaders of the DUP and Sinn Fein to come together again. But that might be easier if Foster yields to pressure from others in the DUP to allow a temporary figurehead to run the administration while she sits out the inquiry into the failed renewable energy scheme.