David,
I don't think Obama will follow your lead because: (a) he mostly avoids specifics on corruption/ethics issues with the Bush administration, probably because it tests badly; and (b) he is avoiding taking on Palin personally, probably for the same reason (and that he'll leave those attacks for surrogates).
How's this instead:
"John, Bill Ayers is a man whom I've known only since 1995, who lives in my neighborhood in Chicago, and with whom I sat on a school reform board created by the late conservative philanthropist Walter Annenberg. I knew nothing of Ayers' 1960s background until more recently, and earlier in this campaign I already repudiated his actions -- those awful things that he did when I was only eight years old and I didn't know him.
Three independent fact-checker organizations have all looked into your allegations and concluded that they are false and over-the-top.
Why you're raising this issue now is completely transparent: your own campaign said that if the campaign is about the economy, then you lose election. So you're trying to change to topic to something else -- anything else, even this muck -- just to avoid talking about the economy.
Why wouldn't you want to talk about the economy? Because a few weeks ago, you said, yet again, that "the fundamentals of our economy are strong." Later that same day, the Dow Jones index plummeted four percent, and it has nose-dived around 20% in the last month since you made that ludicrous remark. The credit markets have frozen so badly that blue chip companies can't get the most basic loans that they need to pay for operations and payroll.
Seniors are worried about losing their retirement savings in the last year, and you talk about this tenuous guilt-by-association instead.
Auto workers in Michigan and Ohio are scared that they will lose their jobs, and you want to talk instead about some guy I've only interacted with informally a handful of times.
Our state and local governments are scrambling to hang on in this crisis, threatening everyone's schools, health care, and the long-overdue repairs of our infrastructure -- and you want to keep changing the topic back to this guy who I hardly know.
The economy is at a precipice and you're just showing everyone again and again how out of touch you are about it.
It's time for you to start talking about the economy for once. The American people are worried about the economy, but you're doing everything you can to cover your ears while shouting this guy's name again and again. Listen to the people of this great country and start talking about their issues instead of this rubbish.
Try running an honorable campaign instead of the slime you've been slinging the last couple of weeks. The American people deserve better than this."