FWIW, his lawyers have produced his argument. It's available as part of the IL election board decision package.
Almost everybody has an opinion about the issue and agrees it's an unsettled issue. For me, just my personal view, is I'm uncomfortable with a foreign-born person with one non-citizen parent and being a resident and citizen of another country for the first few years of his life being "natural born". The longer the issue drags out, the more people will become solidified in their personal views.