It is odd to think of David Cameron as the most electorally unsuccessful Tory prime minister in history. He has the air of a winner, and certainly behaves like one. He is redefining British politics, leading the most reform-minded government since Attlee's, and is undeniably the Conservative party's greatest asset. So what happened to that 22-point opinion poll lead he had in the summer of 2008? Why did he fail to win a majority, in perfect electoral conditions? And what might come next? Three books seek to provide an answer.

Michael Ashcroft's verdict came on election night, in a boat chartered by the BBC, when he blamed the televised leaders' debates for turning "everything topsy turvy". He said no more and started work on his eagerly awaited pamphlet, Minority Verdict. Those who expected it to tear the coalition to shreds as a farewell gesture will be disappointed. "This will not be a hatchet job, or some kind of explosive insider account," he warns in the introduction – a sentence that may make a good many readers put it down immediately. The noble lord is, alas, as good as his word.

Ashcroft is a billionaire who could do anything with his life: for the past few years, he has chosen to spend it hounding Labour MPs in marginal seats. It was his efficacy, not his money, that Cameron valued. His extensive opinion-poll research and clinical manner come across in what is, in effect, a 144-page debriefing note disappointingly stripped of anything that might sniff of malice. His most censorious sentence says the Tory victory disappeared down "the gap between the change people wanted and the change people thought we were offering".

There was too much emphasis on attacking Gordon Brown, he said, and not enough explanation of what the Tories stood for – leaving voters with their own (mainly negative) suspicions. Rather than find fault with Cameron, he spends much of the pamphlet taking on critics of the Tory campaign (myself included), but he concludes on a rather sombre note. The number of voters who identify themselves as Tories, he says, rose from 24% five years ago to 25% in the last election. More people felt able to lend the Tories their vote, but for tactical reasons. There were staggeringly few converts.

Such a grim prognosis is perhaps why a new Tory MP, Nick Boles, is keen for the Tories and Lib Dems to enter a pact – and seek to govern for the rest of the decade. His book, Which Way's Up? offers an agenda for such a union. It is not really a book about the "future of the coalition in Britain", contrary to what its cover suggests, but a pick of policy proposals which he thinks might suit. As the founder of the Policy Exchange think-tank, Boles has no shortage of ideas and has chosen ones which he thinks represents "the best bits" of both parties. From banning gated housing developments to deporting eastern Europeans, there is intended to be something for everyone.

This time last year, Which Way's Up? would have been seen as a straightforward manifesto of Tory "modernisers". Now, this is presented as a coalition agenda – a form of ideological glue to help the two parties stick together. And Boles is sincere in his declaration that he wants the union to last. Many Tory modernisers regard coalition with the LibDems as the safest vehicle for their agenda. Had Cameron won a slim majority that night, he would be in a tougher coalition – with his notoriously regicidal backbenchers.

More importantly, many Tories regard coalition as a tool to "detoxify" the party in office in a way that (as Ashcroft's book points out) it failed to do in opposition. So Boles's argument is one that might gather momentum. While it can read a little like a policy shopping list at times, there is reason to pay attention: Cameron does have an odd habit of stealing such ideas, in their entirety, from such books, so many of Boles's proposals may be tomorrow's white papers. Especially if they are likely to bind the coalition further together.

If Ashcroft has written a campaigning manual, and Boles a policy prescription, Dennis Kavanagh and Philip Cowley have penned something of a political thriller. The British General Election of 2010 tells the stories that Ashcroft withheld and Boles probably never knew, the inside story from all three campaigns about what was – by all accounts – a three-way car crash. The book is distinguished by the quality of its sources: the ministers, aides and strategists who open up to these academics in a way they might not to journalists.

The best chapter is "Losing it in January" which details the launch of the Tory campaign and its flaws. George Osborne was, in theory, the election co-ordinator, but "regarded himself as a chairman, rather than director of the group". The impulsive Steve Hilton would launch a phrase (like "great ignored"), then discard it the next day. Andy Coulson, the press chief, was at loggerheads with Hilton. Cameron stood back from it all – and the result was an all-too-discernible lack of direction. Cameron's standing amongst the electorate fell, as the Tory campaign muddled along.

The other two campaigns were just as chaotic. Mandelson is quoted complaining about Labour's lack of message and the campaign chief, Douglas Alexander, was amazed that they didn't lose more seats. Yet Labour's despair we know about. This book also takes us behind the scenes of the Liberal Democrats. The party spent nine months writing a manifesto, one insider says, "and managed to come up with just one policy that wins votes, two which lose votes and about 7,000 policies about which no one gives a flying f…"

It is unusual, in a book by two academics, to find passages where four-letter words outnumber opinion poll statistics. But both are the language of election campaigns – and Kavanagh and Cowley convey it, vividly and faithfully. They agree with Ashcroft that Cameron's main failure was failing to detoxify the Tory party. People had turned away from Labour, but had not been given a reason to turn to a Tory party they still rather mistrusted. And might they next time? Ashcroft hopes so, Boles rather hopes not and Kavanagh and Cowley say no one has a clue. If the last few months have taught us anything, it is that prediction is now a fool's game.