The dems are trying desperately trying to spin this but it’s already out there. This is why, (I believe,) Bush wisely is staying away because Obama desperately needs to portray himself as the man here, if Bush had showed up Obama would treat him like he has Ryan, Paul, SCOTUS and others.
Another reason for Bush not to show up is, what happens if the crowds cheer Bush louder and longer than Barry?
Embarrassing for everyone, more gracious to avoid the situation. Clinton (either) would jump at such a potential to upstage someone.