With polls pointing confidently to a Tory landslide in June's election, some will wonder whether Tim Farron's decision to rule out Lib Dem involvement in a coalition government is anything more than wishful thinking. As things stand, the possibility seems remote to say the very least. Indeed, a simple reading of the situation would suggest that Mr Farron has been able to make the decisive move precisely because there is no chance of anything other than a Conservative majority. Time will tell.

Nevertheless, it is clear that some prospective Liberal Democrat supporters will welcome the clarity brought by the announcement. There has been chatter among commentators – and some politicians – about the potential success of a “progressive alliance” of the three main opposition parties, the Lib Dems, Labour and the SNP, or at least the first two of those. But as Mr Farron recognises, Jeremy Corbyn is such a divisive character that talk of any sort of pact is more likely to undermine the Liberal Democrats' base than to strengthen it. The same is true of a possible pact with the SNP. As for coalition with the Tories, the two parties diverge so strikingly over Brexit that a deal would be impossible to envisage even in the unlikely event that Theresa May finds herself with a minority of the available seats.

Moreover, while Labour will be desperate to shift the focus of their election campaign away from the subject of EU withdrawal, for the Lib Dems it is a unifying factor – both within the party and among target voters. By positioning itself squarely as the party of choice for those who do not wish to see Brexit at any cost, Mr Farron has made a clear pitch to the many who voted against EU withdrawal last year and to Brexiteers who didn't anticipate the kind of hard departure the Prime Minister appears to have set her sights on. In this context, the Lib Dems' offer to the electorate is much more clear-cut than Labour's.

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For the Liberal Democrats, then, any discussion about coalition is a distraction. By ruling it out now, Mr Farron has also done his best to undercut Ms May's attempt to present the general election as a choice between her own “strong and stable” leadership and a messy coalition government led by Mr Corbyn. That is plainly a false dichotomy and Mr Farron is wise to hammer home the point.

Still, it is important that the Lib Dems' anti-coalition stance during this election campaign, apt though it may be in the current, unusual circumstances, does not become a long-term mantra for the party. For years it was more or less satisfied to be a party of perpetual resistance – not only to the government of the day but also to whichever of the big two provided the primary opposition in Parliament. Sure enough, the experience of government between 2010 and 2015 – and the disastrous election result which followed – led some activists to conclude that it was better (and easier) to protest from the sidelines than to get down and dirty with the business of actually running the country.

Yet it is important to remember that the Liberal Democrats played a significant part in preventing David Cameron from taking the country on a lurching journey to the right during those difficult coalition years. Raising the income tax threshold, championing apprenticeships and making the green agenda genuinely mainstream were all significant Lib Dem achievements. And while the tuition fees debacle proved costly at the polls in 2015, Nick Clegg's decision ultimately to back the changes was not only right but showed that his party could make tough, unpopular decisions. The present government showed notably less courage over the NICs furore which followed the Chancellor's Budget in March.

Whether formal coalition is the best way to bring stability to a hung parliament remains a matter of debate. One of the difficulties shown up by the Conservative-Lib Dem alliance was the lack of flexibility on key issues not determined at the outset of the partnership. Informal pacts made on a policy-by-policy basis may prove more effective if and when we next find ourselves governed by a party which does not enjoy a Commons majority.