Calm down.
Floating voter advocates like you, forget to mention one thing, if floating voters decide elections, then we have a dictatorship of the floating voter, they are, in effect, the electorate.
If a party has a set of policies that do not appeal to the floating voter, they must do one of three things.
1. Confine themselves to being in permanent opposition, a campaigning group. That's the ideological purity bullshit you accuse me of, depriving the working class of an authentic champion by clinging like a crazed zealot to outmoded Marxist principle.
2. Change tack, triangulate policies, steal the goodies the opposition has and wrap them in your own party colours as Bill Clinton did with the Democrats, or go a stage further and create a completely new party as Blair did with New Labour, with policies cobbled together by focus groups to appeal to floating voters in the certainty that "old Labour" voters will fall in line, desperate to get in to power and do at least some good....I think it's fair to say that's your position.
3. Stick with the founding principles of your party, in fact re-discover them for a new generation, be confident and bold in advocating them and convince people they are the right set of principles, the right policies for themselves, their families, for their fellow citizens and for future generations and in so doing move the debate in your direction, move the middle ground, don't follow what you think floating voters are thinking, tell them what you think and if your are sincere a sufficient number will float to you.
It's what Thatcher did, she shunted the middle ground to the right and since the 80's guys like you and SWP have screamed that no party can succeed unless they tack to the right. New Labour bought in to this. Effectively New Labour set its camp in the fields of the right and tried to see what it could do there, but in the end, despite squeezing the odd concession here and there, all it ended up doing was to become the very thing it replaced, the Tories.
This is Tony Blair...
"I wouldn’t want to win on an old fashioned leftist platform. Even if I thought it was the route to victory, I wouldn’t take it."
What he is saying is that even if the electorate would vote for such a platform, he, Tony Blair, would not take it! Who's the ideological zealot here?