Bush Snr built this clown-op shit-show and he's proud of it. That's why he's in the middle. Obama is the one physically projecting furthest forward. He's in charge of the clown-op now. Carter and Bush jnr are mirroring his gestures. They accept that they report to Obama. Slick Willie is not mirroring, indicating he his own man. He is outside of Obama's power-structure.
Gaga behind the Bush duo makes it look like she's their handler. So although Obama is now in charge, it may not of been a hand-off so much as a power-grab.