Perhaps the Bobs did add that line in there as a joke, as Jane Wyman was more famous of an actress than Nancy Davis was. The most common explanation given for Doc's mistake is that he maybe just wasn't as alert on the happening of the Hollywood industry.

However, I just thought of something else. What if Doc did know that Ronald Reagan had divorced and remarried - and, in addition to him being an actor, Doc also found the idea of him being the US President to be ridiculous because of his marital status? So, as a result, maybe Doc was pointing out that the only way for him to have a chance would be to remarry his first wife?

That might be a possibility, too. :)

I think I pointed that out before about Reagan's marital status.

I know that, to date, he's the only US president to have gotten a divorce. Than again, Doc doesn't really seem like the kind of person to be up on the whole acting business.