Explain how we got into the Financial Crisis. How the housing bubble was the root of all this. Explain Fannie and Freddie's role in this. Explain how some people tried to correct the Fannie problem in 2005 but was blocked by Fannie's friends. And how you are going to deal with this when you become president. That's all the public wants to hear right now.
There's no need to point out the democrats and Obama's obvious ties to Fannie, to avoid the appearance of politicizing this thing. But if Obama brings up Rick Davis, then you respond by bringing up Raines, Johnson, and the Fannie contributions they used to buy Obama.
But if Mccain wants to avoid even talking about this issue, then it's a landslide victory for Obama in 2008.