Does David Cameron understand the British electoral system? I just ask, because today’s story in the Sunday Times suggests he doesn’t:

"Senior Tories say the prime minister is planning to declare victory if he gets the most seats and votes on Thursday. He is expected to give a statement in Downing Street on Friday if the Tories are “clearly the largest party” — forcing Ed Miliband to strike a deal with the Scottish National party (SNP) to bring him down."

Under the rules of first past the post – a system that, unlike Ed Miliband, Nicola Sturgeon or Nick Clegg, Cameron campaigned to keep just four years ago in a referendum – it doesn’t matter one way or another if you are ahead in the popular vote, or if you have more seats than any other party for that matter. What matters is your ability to command a majority of parliamentary seats for your laws and measures.

Unless the polls are wrong, it looks unlikely that David Cameron will have a majority of any kind in the House of Commons. Labour, obviously, won’t vote to keep him in Number 10. Neither will the various separatist parties – Plaid Cymru, the SLDP and the SNP – and friction over an In-Out referendum remains a serious block to aother arrangement with the Liberal Democrats. Any deal with antother party must pass the Liberal Democrat “triple lock” of parliamentarians, the Federal Executive and the party’s membership. One well-connected activist says that, for it to have any hope of passing all three, Tim Farron, Vince Cable and Lord Ashdown will all have to back it, and “even if all those stars align”, the chances of a deal being approved by the membership, bruised by a half-decade of electoral losses, are “no more than 50:50”.

Obviously, a government-in-name-only, unable to pass many of Ed Miliband’s most radical measures, is some distance away from the radical administration that those behind the Miliband project dreamed of. Already, senior staffers are drawing up lists of policies that could be achieved without legislation, and goodies that could be offered to the Liberal Democrats in order to get that party on side for key votes. But it would, nonetheless, be a government. Cameron can declare what he likes on the morning of May 8, but it won’t change the arithmetic.

It would be a fitting final end for the Tory campaign. Over the course of the last few months, I’ve heard senior Conservatives compare their battle with John Key’s 2014 re-election, when the far right party collapsed over the final weeks, to Benyamin Netanyahu’s against-the-odds triumph earlier this year, and to Steven Harper’s re-election in 2011. (Both Netanyahu and Harper exploited the idea that their left-wing opponents would ally with parties that would imperil the territorial integrity of the country as a whole, which the Conservatives hope they will be able to do with the threat of a Labour-SNP deal.)

Now they’re briefing that, if all that fails, they’ll channel Al Gore in 2000. Like Cameron, Gore won a majority of votes cast, and was only denied victory by the vagaries of the American electoral system. Gore declared victory – but George W Bush won. Percieved “legitimacy” mattered less than the rules of the game.

There’s another lesson, here, too. The Democrats spent four years saying that Bush the Younger was illegitimate – bumper stickers with the slogan “Re-Defeat Bush ‘04” became bestsellers. They referred, only half-jokingly, to “President Gore”. But they failed to come up with a compelling critique of the Bush administration, beyond complaints over legitimacy, and Bush was duly re-elected in 2004. If the Conservatives make “legitimacy” their argument over the next five years, Miliband may find it easier than he expects to hold onto power in 2020.