The term “Super Tuesday” goes back at least to 1984, but since there were three of them that year it doesn’t really fit the modern usage. (Thanks to Wikipedia for this interesting discovery.) The current usage dates from 1988, when the Democrats first concentrated a large number of primaries (particularly in southern states) on a Tuesday early in the season, with the aim of settling quickly on a moderate nominee.

It didn’t work as planned; the nominee was still in doubt for another month, and the centrist southerner Al Gore lost out to the more liberal northerner Mike Dukakis. But it worked that year for the Republicans (even though their “Super Tuesday” wasn’t as big), who quickly settled on George Bush snr, and since then it has decided the issue every time: no party has been in any real doubt about its candidate beyond Super Tuesday.

Odds on that will be the case in 2008 as well. While commentators love the idea of a “brokered convention”, where no candidate has a majority locked up by the end of the primaries, it hasn’t happened since 1976 (when Jerry Ford narrowly held off Ronald Reagan for the GOP nomination). This year, with each party already down to a two-horse race, Super Tuesday should anoint clear winners – almost certainly for the Republicans, where John McCain looks to have an unbeatable lead; less certainly for the Democrats.

What’s changed since the 1980s is the timing: the primary season used to start in February, with Super Tuesday in March. This year it’s at the beginning of February, a full nine months before the election. In 1992, for example, Bill Clinton broke away from the pack on Super Tuesday, 10 March – four months before his party’s Convention, which began on 13 July.

But this year, the Democratic Convention is not until 25 August, with the Republicans a week later. That means the presumptive nominees will have six and a half months in limbo: campaigning, of course, but without yet really being the candidates (and therefore not having to abide by certain spending limits, which is one reason the parties have adopted this strange timetable).

All this takes the system even further away from its roots, where the primaries were the curtain-raiser to the Convention, which was where the action was, and the real election campaign only began afterwards.

What’s more, if one party should happen to have a race that’s so close it goes right up to the Convention – and the possibility of that happening to the Democrats this year can’t be ruled out – it means the other side will have had half a year’s head start.