There is an old cliché – coined by US Senator Daniel Moynihan – that everyone is entitled to their own opinions but not their own facts. This was in my mind when I read Jackie Baillie’s pitch to become Scottish Labour’s next deputy leader.

In it, she charted a course for the future of the party which dismissed out of hand the attempts made under Jeremy Corbyn and Richard Leonard to win back those who voted Yes in 2014. “People don’t join the Labour Party because they want to endlessly debate the constitution,” she said, “it’s not in our DNA.” This is in keeping with a broader effort to write off the 45% of Scottish voters who went for the SNP in the last election, more than a million, many of whom were working-class. Supporters of independence – even those who once voted for us – should not be encouraged to return to Labour.

This should worry us, because Scottish Labour needs these voters. It is time for the party to fundamentally reflect and reform, instead of continuing to play into the hardcore Unionist politics which has proven to be a dead end. We have to be clear on the roots of our decline and we have to face a bitter truth: we were defeated by the SNP narrowly in 2007 and comprehensively in 2011 not just because of a surge of atavistic nationalism, but because the Scottish people did not support the policy platform we put forward, did not trust our elected representatives to deliver and did not believe the Labour Party would best fight for them and their families.

Such a lack of trust and a concomitant lack of support can only be explained with reference to our record in government, at both Holyrood and Westminster. Yes, we did some progressive things, but we were staid and the idea of creating a peoples’ or workers’ parliament was anathema to the Labour campaigns of 2007 and 2011. Of course, it is worth noting that both these election campaigns were directed and staffed by avowedly New Labour figures and the policy platforms we offered were, to put it mildly, neither inspiring nor radical.

The spectre of Better Together is often invoked in explanations of Scottish Labour’s electoral decline, and this is not entirely wrong. But we have to see it as a symbol of a broader failed political approach. The referendum was a tipping point for too many people who had previously supported Labour. Put simply, the Scottish Labour experience has been similar to that of social-democratic parties in Greece, France and Germany.

The Scottish party became divorced from the working-class people who had founded it and was punished by them at the ballot box. It is remarkable that while the SNP have used their position in the Scottish government to retain consistently high opinion ratings, Scottish Labour’s near-decade long tenure in the Scottish executive produced successive decreases in both seats won and overall vote share. (These things overlap, given the proportionality of the Scottish electoral system.)

Over a number of decades, from the election of the ‘fighting fifty’ Scottish Labour MPs in 1987 who stood against Thatcher, through a constitutional convention that ultimately paved the way for the Scottish parliament, to the ‘Yes-Yes’ referendum vote, Scottish Labour successfully acted as the champion of Scottish interests in the face of uncaring Tory governments.

That strategy began to crumble in the New Labour years as frustrations over issues including the Iraq War, Private Finance Initiative (PFI), what Tony Blair euphemistically referred to as a ‘public sector reform agenda’ (privatisation), the introduction of tuition fees and the inhumane treatment of asylum seekers, meant that, in the eyes of many of our core supporters, Scottish Labour was seen to represent the interests of Westminster to the Scottish people rather than the other way around. As James Tilley and Geoffrey Evans have demonstrated, this is in line with growing perceptions among working-class voters that the ideological differences between Labour and the Conservatives had narrowed under Tony Blair.

In by-elections like Dunfermline and West Fife in 2006, where the Liberal Democrats overturned a Labour majority of more than eleven thousand, in Glasgow East where the SNP overcame a Labour majority of thirteen thousand, and in the advent of the SNP minority government in Edinburgh in 2007, the depth of dissatisfaction with Labour’s record was made visible.

By the 2015 election, the SNP had successfully positioned itself to the left of Labour. It used issues which held real symbolic and historical resonance for the Scottish labour movement (such as the presence of Trident on the Clyde or, indeed, the protection of the devolution settlement), as well as the crucial issue of austerity, to gain leverage. The SNP was able to contrast its modest but real rises in public sector spending to both the Tory and Labour approaches of continued austerity (which would, admittedly, have taken place at very different rates) to indict an uncaring Westminster elite, remote from the concerns of ordinary Scottish people’s lives. Better Together was perceived as the final, potent symbol of an out-of-touch establishment.

The consequences were severe, and the result was unequivocal. On a swing against us of 17.7%, Labour lost forty of its forty-one seats, retaining only Edinburgh South, a constituency containing both some of the most affluent areas of the country and one of the highest densities of those who voted ‘No’. It was no coincidence that one of the seats Labour lost by only a slim margin was another of the country’s most affluent – Jim Murphy’s East Renfrewshire, which contains Glasgow’s wealthy southern suburbs. Looking at what remained of Scottish Labour’s electoral coalition after the massacre of 2015, it was disproportionately self-identified unionists, disproportionately middle-class and disproportionately elderly.

Labour lost more than three 325,000 votes from its 2010 tally. It is the biggest drop in national vote share that Labour has suffered in Scottish electoral history. In a little noticed feature of that election, a very substantial majority of the near quarter of a million centre-left voters who abandoned the Scottish Liberal Democrats due to the coalition in Westminster went to the SNP. This was in contrast to their English counterparts, who enabled Labour to pick up seats like Norwich South, Birmingham Yardley and Hornsey and Wood Green.

Scottish Labour collapsed in some of its oldest strongholds, places where it was once joked that a monkey in a red rosette could have secured election. In Glasgow North East, then the fifth safest seat in Britain, on a swing of 39.3%, the SNP overturned a Labour majority of nearly sixteen thousand to take the seat. In Coatbridge, Chryston, and Bellshill, the SNP turned a Labour majority of twenty thousand into an SNP majority of eleven thousand.

By almost every metric, the 2015 election in Scotland meets the definition offered by the American political scientists V.O. Key Jr. and Walter Dean Burnham’s theory of a “critical election”: one in which “majority parties become minorities; politics which was once competitive becomes non-competitive or… hitherto one-party areas now become arenas of intense partisan competition; and large blocks of the active electorate… shift their partisan allegiance.” Indeed, it makes more sense to read the 2017 election, where Labour won an additional six seats in Scotland on a slightly increased vote, and 2019, when the SNP once again surged, through the prism of 2015 and the differential turnout of SNP voters. Ailsa Henderson and James Mitchell have shown that around one in ten of the SNP’s 2015 voters stayed at home in 2017.

So Jackie Baillie is not wrong to insist, as she did in her recent Scotsman piece, that Scottish Labour must change if it is to have any future. But she is wholly wrong in insisting that any progress can come about without appealing to the hundreds of thousands of former Labour voters who voted Yes and who have voted for the SNP since. This would be the English equivalent of saying Labour has to write off seats like Morley and Outwood or Bolton West.

To be frank, if this is Jackie’s preferred electoral strategy, it is little wonder that Richard Leonard chose to remove her from his shadow cabinet. The Ulsterisation of Scottish politics which she implicitly supports will benefit only the Scottish National Party and the Conservative and Unionist Party. In contrast, Matt Kerr is supported by the evidence when he says that the electoral coalition Scottish Labour has to build is one that includes Yes and No voters. That’s why he has my full support in the Scottish Labour deputy leadership contest.