Who was Allen's replacement in 2006?
You're making my point here. He didn't step down and was defeated. As the incumbent, no primary runner-up was available because no primary was held.
In 2012 (and for the record here, I voted for Jamie Radtke in the primary), Allen and the "macaca" issue from 2006 are known entities .. he's running against a popular former governor and is neck-and-neck.