In light of Sen. Obama apparently turning down Sen. Clinton's offer of a Lincoln/Douglas style debate. (I understand why he said no, she is basically done and the debates would have done him no favors). I tried tracking down something I seem to recall from his senate campaign, how there was talk that he was going to Lincoln/Douglas with Jack Ryan up to six times around the state. I was able to find some blog posts I had done about it but the news stories that came up on google were almost all pay to read, so suffice to say I didn't read them
I know it's a lot of if's but if Ryan didn't have his issues and stayed in the race the Obama/Ryan debates would have been interesting and may have given a lot of insight into Senator Obama.