All this is very self-important. The Sun likes to think and say that it wins elections for whichever party it supports - it's an equally convincing argument that The Sun supports whoever it thinks its readers support. Lots of data here
The Sun recommended that its readers vote Labour for the past three elections, but it never supported Labour. Its reasons were always hedged and reluctant, and often negative - based on the disarray in which the Conservative Party found itself. Essentially, The Sun supported Tony Blair and his clique, rather than Labour values. The Sun was and is racist, selfish, consumerist, nationalist, anti-green, homophobic, militaristic and misogynistic. For a few years, New Labour captured the Labour Party and catered, shamefully, for these positions. The Sun didn't change - Labour did, and deserves opprobrium for its shameful capitulation to the worst aspects of British culture.
Will readers of The Sun be better off under the Tories? I wouldn't think so. They're working class individualists - not natural supporters of the Etonian land-and-inherited-wealth toffs who really, really don't give a fuck about the poor. Sure, they'll toss some selfish, racist red meat to white van man, but they don't have the interests of the working class at heart. Sun readers like the NHS for instance - the Tories hate and fear it.
But that's irrelevant - The Sun and all the News International papers don't care about their readers either: their writers care about the opinions and commercial interests of Rupert Murdoch, who wants to run the world and wants to run it as a capitalist oligarchy free from competition by boring old state-funded, objective BBC - exactly what the Tories will give him. That's why the declaration was today, and not during the election campaign, as usually happens. It came out the day after Brown and Mandelson made good, fighting speeches. Rather than reporting news, The Sun decided to ruin the Labour conference and help the Tories by intervening in the political process. Mmm…ethical.
Fuck The Sun (sorry, I'm quite angry). It's too stupid to be as evil as the Daily Mail, but it's still a cancer on the public sphere.