Arizona Senator John S. McCain has postponed today's scheduled appearance at the ARCO Forum after accepting an invitation to sit with the family of Texas Governor George W. Bush during tonight's presidential debate.

McCain was to address the forum at 4 p.m., but his assistants could not work out a way to get him to St. Louis, Mo. in time for the debate, which begins at 8 p.m. EDT.

Bill White, director of the forum, said McCain would likely schedule a rain check appearance for the weeks following the Nov. 7 election.

IOP staff members were alerted early this weekend to the possibility that McCain would postpone his visit, White said. They remained in close contact with Rick Davis, the former campaign manager for McCain who is now a fellow at the IOP.

"There was a lively discussion [among McCain's staff] this weekend as to whether it was feasible to change the schedule," Davis said.

One early suggestion was McCain would use a state police escort to speed off to Logan Airport following his IOP appearance, hopping on a direct flight to St. Louis.

But that would have cut it too close, his staff decided, so McCain was forced to cancel.

"There was no way he could make it from the Kennedy School to St. Louis for the debate," said Adrianne Kaufmann, an IOP spokesperson.