Nick Clegg's decision to call a referendum on the voting system on the same day as local elections backfired disastrously, the Liberal Democrat inquest into the party's crushing double defeat has concluded.
A report to the party's annual conference in Birmingham later this month says the council elections turned into a "perfect storm" because the referendum on the alternative vote (AV) also took place on 5 May.
Although David Cameron wanted to delay the AV vote until this autumn, Mr Clegg insisted it was held in May in the hope that elections to the Scottish Parliament, Welsh Assembly and English councils would boost the turnout – and the prospects of a Yes vote. In the event, AV was rejected by 68 to 32 per cent and the Liberal Democrats lost 700 town hall seats. With hindsight, the report concludes, the double poll meant that Liberal Democrat activists were unable to give enough time to the "Yes to AV" effort. It also prevented the seconding of staff to the referendum campaign, took media airtime away from the elections and allowed Labour supporters to "kick the party twice".
The report says: "Turnout among Conservative and socially-conservative Labour voters was at general election levels, driven out in consequence of the AV referendum. A huge trade union campaign in Labour-leaning areas targeted the party leader [Mr Clegg] personally and viciously."
A simultaneous AV referendum also meant that Mr Clegg's party got little or no credit from Tory supporters. "Conservative voters satisfied with the Coalition were reluctant to vote tactically for their coalition partners in Lib Dem/Labour marginals, in no small part because of the vociferous rivalry between the two parties in the national referendum," the report says.
The review by James Gurling, chairman of the Liberal Democrats' campaigns and communications committee, will be discussed on 17 September, the first day of the party conference. Some activists claim his inquest has been kept deliberately low-key to spare Mr Clegg's blushes. Many grassroots members remain angry about the defeat and may criticise the leadership at the conference.
The document admits: "Many dedicated community activists lost their seats through no fault of their own, and in the face of exemplary records of personal service. The challenge now is to ensure that the activist base which supported them is not lost."
The report concludes that Liberal Democrat achievements in government "had not been successfully communicated... the impact of the debate on tuition fees and NHS reform undoubtedly played a part".
It appears that some voters told Liberal Democrat campaigners on the doorstep that they would back the party but then failed to do so. The report says the Liberal Democrats may have to change their approach to canvassing now that they share power nationally.
Allies of Mr Clegg believe some criticisms are out of date. Since May he has adopted a more aggressive approach inside the Coalition, distancing his party from the Tories on some issues and trumpeting Liberal Democrat achievements such as changes to the Government's health reforms.
But as MPs debated the Health and Social Care Bill yesterday, the Social Liberal Forum, a pressure group on the left of the party, called for further changes to the legislation and for a full debate at conference. Evan Harris, a former MP, said the revised Bill would not prevent the "marketisation or fragmentation" of the NHS.