Tactical voting over Brexit will define this general election, but it's getting harder to know where to place your vote

Last week, Labour was toying with the idea of a second referendum on Brexit, once the terms are agreed. By the start of this week that option had apparently been closed off by the party. Then Sir Keir Starmer, on some interpretations, restored it by (as the phrase goes) refusing to rule it out, which is to say he didn’t propose to say anything about it when the text of his speech was pre-released.

Then he did say something – and he ruled it out. Twice. The policy, such as it is, could gyrate some more during the course of the next six weeks.

So, we know where we are with Labour: it is confused about a second referendum (or, alternatively, a “meaningful” parliamentary vote) but is clear and united in wishing to have a generally nicer, softer Brexit than the Government proposes, whether or not the tantalising prospect of remaining in the EU via a second referendum ever does come to pass.

In concrete terms, Labour is in favour – rightly – of a unilateral guarantee to EU citizens who have made homes and are bringing up families in Britain; of retaining the EU’s charter of fundamental rights; of prioritising the health of the economy over migration. Those are not trivial details. Labour is plainly more pro-European than the Conservatives because that is where the instincts of the bulk of its members and MPs lie, just as the instincts of the Tories are to cut taxes even if they are sometimes forced to increase them. By long acquaintance, voters are familiar with these behavioural biases.

Importantly, Sir Keir says that he does not share Theresa May’s judgement that “no deal is better than a bad deal”. This is on the entirely reasonable and logical grounds that “no deal” – the default to World Trade Organisation rules – is by its own definition the minimum degree of free trade and economic freedom that is possible between any WTO member states or organisations. Anything else in the way of a Starmer-negotiated UK-EU deal, even if it only extended to rules about bananas, would be an improvement.

All of which leaves Remain supporters in something of a quandary. If, as Tony Blair, Lord Mandelson and Open Britain believe, Brexit is the transcendent issue in the 2017 general election, then voters should ascertain the views of the candidates standing in their constituency, weigh their chances of defeating the more Eurosceptic of the mainstream runners and vote accordingly.

Leaving aside the “prisoner's dilemma” aspects of such calculations – that different voters will form a different view of the necessary tactics and cancel each other out – that is asking a great deal from people who think about politics, even in today’s febrile climate, comparatively little.

Mr Blair’s call for tactical voting does open the possibility of this former Labour leader – and the last to win a general election a sobering 12 years ago – might actually vote Conservative or Liberal Democrat in whichever constituency Mr Blair ends up casting his ballot. More broadly, it carries an unspoken mortal threat to Labour Brexiteer Kate Hoey in Vauxhall, where a more gentrified electorate has diverged from her views on the big issue of Europe and the smaller issue of a “garden bridge” over the Thames (all politics is local, after all). She is vulnerable.

The call for tactical voting also suggests that the few pro-EU Conservatives in, for example, Clacton might be best off voting for the Labour Party if the Tories put up a strongly Eurosceptic candidate to win back the Ukip vote. Meanwhile, pro-EU Labour and Tory voters in Carshalton and Wallington would make best use of their votes by voting for the Lib Dem incumbent MP, Tom Brake.

Given that the Liberal Democrats are the most pro-Remain of all the main parties, it makes sense for a large proportion of Labour and pro-EU Conservatives to vote for them where they are amounting a credible challenge to a pro-Leave Labour candidate or, more often, a Tory Brexiteer (as almost all are nowadays). Tim Farron would thus be the major benficiary of Mr Blair’s tactical wisdom, and Jeremy Corbyn the main victim. Indeed, by the same Blairite reasoning, pro-EU Labour supporters should vote for a moderate pro-EU Conservative to defeat Jeremy Corbyn in Islington North, as the Conservatives in 2015 managed to come second (albeit poor one) in that seat.

The issue of voting for a pro-EU SNP member in preference to, say, a pro-UK but anti-EU candidate might be more perplexing for some voters – not to say dizzying in its kaleidoscopic complexity. Assuming that the various candidates actually did keep their word once they’d been introduced to their party’s team of whips, that could produce a substantial bloc of moderate voices in each of the main parties that would at least restrain the hard-liners who are overrepresented on the Conservative benches, and by whom Ms May does not wish to be held hostage, in any case.

There is one other player in all of this: the remaining EU. The unstated assumption in Sir Keir’s proposals is that the EU would agree to a so-called “soft” Brexit. They may do so; but they may not. It takes two to make a deal. The possibility that they would not has been acknowledged by Ms May, and the logic that that means exclusion from the single market and much else has been accepted by her. What Sir Keir and his Labour colleagues have not been able to accept is that a refusal from the EU to offer a better deal should mean that Britain would be better off staying in the EU. Nor is Labour entirely clear on whether or not it wants to set a limit on the free movement of labour from the EU, and on what terms that migration should take place.

Sir Keir, as ever, did his skilful best with a tricky brief, a divided party and senior colleagues who apparently keep wobbling about immigration. At least he succeeded in making Labour sound more positive about the EU than Mr Corbyn generally does. Not a towering achievement, but a useful one nevertheless.