He's likely a young aide that travels everywhere with the President and right by his side at all times, ya think? Doesn't look Secret Service.
Perhaps you are right. I don't think he looks like Secret Service, either.
I think he may be the young man who is replacing Blake Gottesman as his personal aide. I read that Blake was going back to college. Blake is the guy that comes out and affixes the presidential seal to the podium right before GW is going to speak.