I beg to differ, if the following is accurate:
the
nomination of any person to office
may be contested in the circuit court
by any elector or any taxpayer
then it says that the nomination to any person may be challenged; it does not restrict the whom of who is nominated, or the how.
The Office of President of the United States is an Office, obviously. So it, too, must be challengable.
There could be argument that Obama has not won the primaries (or has he? I don't know) and is therefore not yet nominated
perhaps you should challenge the eligibility of the electors as being obviously insane to have their names on the ballot for obama in the first instance.