I found an article from the Washington Post. This little blurb from the middle of the article sums up the differences between McDonnell and Deeds quite nicely. I've added emphasis as needed to highlight the pertinent text.
I don't have a cite, but from what I remember reading about McDonnell's explanation for the "one gun a month" position change is that the federal background check laws were changed after his initial support for the law, and therfore, that restriction is no longer needed.
If anyone has a link to some source that documents that, please feel free to post it.
Former Virginia governor L. Douglas Wilder, a Democrat, pointedly declined to endorse Deeds in that campaign [the AG race in 2005 - TFred] because Deeds, as a delegate, had refused to support legislation limiting handgun purchases to no more than one per month -- a measure McDonnell backed.
But both candidates have gravitated closer to positions generally embraced by their party's base.
McDonnell, for example, now says he supports a repeal of the one-a-month law because computerized background checks and other advances make it unnecessary. In an interview last week, McDonnell also said he opposes further regulating gun shows because statistics show only a tiny number of guns used in crimes were obtained at gun shows.
"I'd say it's a little bit of a misnomer to call it a loophole," McDonnell said. "It's really an attempt to regulate private sales."
But McDonnell touted his work with Gov. Timothy M. Kaine (D) in closing a loophole that allowed the Virginia Tech shooter to evade a ban on transferring firearms to someone with serious mental illness.
"I'm very sympathetic to the victims at Virginia Tech," McDonnell said. "The problem that occurred at Virginia Tech had nothing to do with the gun show loophole."
Deeds, who owns several firearms and has hunted since he was a child, said he understands the importance of the Second Amendment and has no interest in working for broader gun controls except for the gun show loophole.
"For me, everything changed on April 16, 2007," Deeds said in an interview Sunday. "As a father, I felt just a need deep down in my soul to respond to their grief somehow."