The silly season has ended a little earlier than planned in Scotland after Kezia Dugdale, the Scottish Labour leader, resigned yesterday.

There are competing theories as to why she did so: the official version is that she “reassessed her life” after the death of a friend, but there are also suggestions that she was “forced out by JC’s mob” and was facing a leadership challenge.

Over at the Spectator Fraser Nelson supports both stories at once, accepting Dugdale’s stated reasons her decision to quit whilst suggesting that the long-term prospect of a Corbynite putsch may have motivated it. That may be closest to the truth.

Already, the debate over her legacy has started. Nelson argues that she was a good leader, citing the general election result and her abilities as a debater, and Euan McColm believes that she was a higher-calibre candidate than any of her would-be successors.

Isabel Hardman disagrees, and takes a much dimmer view. She highlights Dugdale’s unforced errors on the constitution, which ceded precious ‘Unionist’ territory to Ruth Davidson’s Tories, and her indulging the Left by adopting divergent policy on reserved issues such as Trident.

Worse, perhaps, is the fact that the timing of her resignation pulls the rug from under her moderate allies in the wider Labour Party.

One of Dugdale’s triumphs as leader was to win the right for the Scottish and Welsh leaders to nominate their own representatives to Labour’s National Executive Committee. This very important body has until now been finely balanced between Corbynite and anti-Corbynite members… until now.

Alex Rowley, the interim leader of Scottish Labour, is a Jeremy Corbyn man. According to Stephen Bush, giving him the opportunity to fill the NEC slot “would tip the balance of the party’s ruling executive from hung between Corbynsceptics and Corbynites to a narrow majority for Corbyn.” And right before conference, too.

Nor is this just a short-term boon. According to both Bush and Chris Deerin, whoever succeeds Dugdale is almost certain to be a much stronger public supporter of Corbyn if not an out-and-out Corbynista. As far as the leadership is concerned that will be a clear upgrade from Dugdale, who backed Owen Smith’s leadership challenge after the EU referendum.

All this will be welcome news to Davidson, who may be able to woo more pro-UK voters who have stuck with Labour thus far but are alienated by anything that smacks too strongly of actual socialism. And if an openly non-Unionist candidate such as Rowley wins it would again likely see a fresh wave of defectors as unionist voters abandoned Labour.

Regardless of the extent to which Dugdale can take the credit, Labour is in a better position in Scotland than it expected to be 12 months ago. The SNP are struggling, caught between public opinion and the mismanaged expectations of their base and tired after a decade in office. Voters who backed independence out of left-wing despair at Britain are tempted by Corbyn’s prospects.

The coming leadership battle will be fought out not only between left and right, but between those for whom Labour is a unionist party and those for whom support for the United Kingdom is tactical and mercenary.

It will decide which voters the party attempts to woo (and perhaps more importantly, not woo) ahead of the next Scottish elections. If they alienate the right people, could make the difference in Davidson’s bid to be First Minister.