The Fitzgerald campaign said scheduling conflicts might prevent the Allegheny County councilman from appearing at the event, which was to at 8 p.m. Thursday in's Sewall Center.
Fitzgerald campaign manager Mike Mikus said the candidate also has been booked to appear Thursday night as a keynote speaker at an event for the Allegheny County Democratic Party.
He said the campaign is "trying to see what they can do to make the event work."
Fitzgerald, a Democrat, is running against Mt. Lebanon businessman Raja, a Republican, to replace Allegheny County Executive Dan Onorato in the Nov. 8 election.
A representative for Raja's campaign said the candidate was still planning to attend Thursday's RMU event.
The candidates squared off last week at a forum that the Pittsburgh Area Airport Chamber of Commerce conducted.
Check back with Patch for more information and for coverage of the event.