For convention planners from both parties, there is a unique problem they must deal with that is similar for both sides but carries different challenges as well.

For the GOP, the problem is what to do with George Bush. An unpopular president with the general public, Bush nevertheless enjoys rock solid support with much of the party base. His 30% approval rating comes from rank and file Republicans who would not look kindly on any kind of snub that the McCain campaign might believe would be necessary to generate some distance from the president.

On the other side, the question of what to do with Hillary Clinton is even more vexing. Here the problem is exactly the opposite; how to move Clinton and her supporters closer to Obama without having her (and her husband) dominate the convention.

It is a delicate dance with the highest stakes imaginable. Here's how the GOP will try and handle things:

That is the crux of the Republicans' 2008 convention quandary. If the imagery coming out of St. Paul looks like a McCain-Bush hug fest, the Arizona senator will turn off voters who are through with Mr. Bush and want to move past him. If the imagery looks like Mr. McCain is trying to file for some kind of Republican divorce, it will turn off party conservatives who are already skeptical of Mr. McCain.

So Republicans may just have to grit their teeth.

"The assumption would be that there will be some kind of physical handoff," said Mr. Jones, the former spokesman for both Mr. Bush and Mr. McCain. "I think there is a sense that they would appear together. He is the sitting president; he's still popular among hard-core Republicans; McCain has some issues with hard-core Republicans. Some people will say this was a bad way to play it, but I think it's one of those things where you have to run through it, and do it, and embrace it."

Democrats face a similar quandary this year in figuring out what to do about former President Bill Clinton after the bitter nominating battle between his wife, Senator Hillary Rodham Clinton, and the party's presumptive nominee, Senator Barack Obama of Illinois.

In 2000, when Vice President Al Gore became the nominee in Los Angeles, Mr. Clinton made a grand entrance into the convention hall, winding his way through the backstage maze, his every move tracked by television cameras as though he were a late-night comic or football hero about to run onto the field. "Elvis was most definitely in the building," said Chris Lehane, a former top strategist for Mr. Gore, recalling the moment.

Mr. Clinton and Mr. Gore had a joint appearance in Michigan just before the convention. But by the time Mr. Gore arrived in Los Angeles, Mr. Clinton was long gone, a move that Mr. Lehane said had been designed to "balance benefiting from voters' desires to continue the Clinton approach while allowing Gore to take the torch and emerge from the large Clinton shadow."