The piece merits careful study in newsrooms and by campaigners. Kellner's wise words point in the following direction. (Each of these is nuanced in important ways, and so you need to have read the Kellner caveats to make proper use of this psephological bluffer's guide. I will add a link when the issue is online):
1. The Tories need friends in the north, as well as the south, to win.
2. Marginal voters don't get you across the line on their own if parties have not nurtured heartland votes too.
3. Media chatter about "Worcester Woman" type archetypes is "invariably nonsense".
4. The LibDems could deny David Cameron victory.
5. "Valence" matters more than issues in deciding how most people vote.
The political nerds hold strong positional views on issues, but most voters, and a majority of swing voters, don't: "they care mostly whether politicians are decent, honest, capable and on their side".
6. The polls have improved, but aren't foolproof.
7. Campaigns are unlikely to be decisive ... though "stuff happens".
Kellner cites the 2002 German and 2003 Spanish elections as exceptional elections upended by events.
The most interesting device for thinking about the election battlefield is Kellner's suggestion to think about it as a battle over four zones - broadly the south, the midlands, the north and a western Tory-LibDem battleground.
To over-simplify a bit, the broad idea is that the south will decide whether Labour can win (as it contains 16 of the 24 supermarginals which Labour would need to hold); the Midlands who is the largest party (since it contains many of the next 40 marginal seats; sweeping these would see the Tories ahead), while progress would be needed on the tougher northern and western (LibDem-Tory) fronts for the Conservatives to win an overall majority.
Of particular interest is the analysis of how it will be more difficult for the Conservatives to make gains against well dug-in LibDems than the arithmetic may suggest.
When the Tories last won an election in 1992, the Liberal Democrats took 20 MPs. In 2005 they won 62. Almost all of those 42 are in natural Tory territory. Can Cameron win them back? Probably not ... The Tories face another handicap in the 17 seats won by Margaret Thatcher where they have fallen into third place. Nine of these were won off them by Labour, but have in turn been taken by the LibDems. Alost all are out of reach for the Tories this time around. All in all, it will be surprising if net Tory gains from the LibDems climb above single digits.
Kellner cites the 1979 election when the Tory gain of 8 points and the Liberal loss of 4 would have been enough to take seven of the thirteen Liberal seats had it been matched in those constituencies, but in fact only 3 of those seats fell.
If something similar happens this time, that in turn, requires a better performance from the Conservatives against Labour.
116 Tory gains would give the party a majority of 2 if the party (nominally) begins on 209 seats after boundary changes. Over 25 of those seats are LibDem or Nationalist held.
Despite the warning against Essex Man and Worcester Women type ciphers (and who now remembers William Hague's patronising pitch to the Pebbledash People and myriad other attempts?), Prospect does also contain an engaging piece in which Sam Knight rides the Thameslink line from Beford to Brighton, claiming to be on a quest for the "Thameslink Tories".
St Albans' Tory MP Anne Main may be one to watch in the campaign. Her expenses claims came under scrutiny and she tells Knight: "People will have to pick their poison when it comes to MPs. We're all pretty horrid" ... I ask her if she thinks it will be a clean campaign. "Dirty as hell", she replies.