From "McCain Plans Fiercer Strategy Against Obama" in the Washington Post:
Two other top Republicans said the new ads are likely to hammer the senator from Illinois on his connections to convicted Chicago developer Antoin "Tony" Rezko and former radical William Ayres, whom the McCain campaign regularly calls a domestic terrorist because of his acts of violence against the U.S. government in the 1960s.
But not all that
The Rev. Jeremiah A. Wright Jr. appears to be off limits after McCain condemned the North Carolina Republican Party in April for an ad that linked Obama to his former pastor, saying, "Unfortunately, all I can do is, in as visible a way as possible, disassociate myself from that kind of campaigning."
Wright is ten times as important a figure in Obama`s life as Rezko, and 100 times as important as Ayers. But Wright is off limits
because he`s black. I figured that`s what would happen back in February