About a dozen or so Democratic officials have now signaled that they won’t attend their party’s convention this summer — but auditions are now open for a Democrat willing to take the next step into apostasy and headline the convention of the opposite party.

There’s a special notoriety for politicos willing to cross that line, embodied most famously by Georgia Democrat Zell Miller, who delivered a famous stemwinder at the 2004 Republican National Convention. Several moderate Democrats ruled out the step in interviews with BuzzFeed, but one prominent former Obama supporter said he’d consider it. …

“Artur Davis offers high profile, African American with compelling and positive narrative that could be the surprise of the Rep convention and fall campaign–if only the Romney campaign can recognize his potential to develop and articulate an alternative narrative,” strategist Doug Schoen, a former Clinton pollster who has called for an independent, centrist movement, said in an email.