This is what I think Barack Obama should say:
America is suffering from the consequences of a culture of lies. The lies of the McCain campaign, while shocking in their brazenness (as I noted during the RNC, they work as lies - those applauding them know they are lies and are applauding the nerve of the liars), are themselves just more of the same, continuous with the culture of lying which has brought us not only into a war we should never have waged, but into the economic meltdown happening all around us.
I've been trying to understand, as have we all, how the subprime mortgage crisis was allowed to happen. Greed and regulatory neglect are only a part of it. The other part is a culture of lies set by the White House with its own refusal to come clean on fiscal questions (itself undergirded by a more general disdain for the publicly accepted meaning of words). If the nation lives flagrantly beyond its means, why can't/shouldn't the individual household? If the national debt goes up year after year, why should not individual household debt? If American greatness requires and can disregard such debt, why not the happiness of every individual? Greatness was never built on lying to yourself about your resources, or tricking your neighbors into forfeiting theirs.
We're better than this. We know that living beyond our means will eventually catch up with us. Further and more importantly, we know that living beyond our means means living at the expense of others. That is something we cannot morally afford, as individuals or as a nation. We're better than this.
We are living in a culture of lies. Only the truth can set us free.
It won't be easy. But it's what we need. And it's what our neighbors - in this land and around the globe - as well as our children and their children deserve from us.