That could be better, you've the proportions wrong. I suggest lowering the Bush layer's opacity to line the face up in "sync" to Obama's features. For example, so you place the eyes where Obama's eyes are etc.
Hehe used to pull sh*t like that on my friends all the time, that's how I got good at working with Photoshop. A pretty old one that you might not even find funny because you don't know the people, but it's just a fun picture to mess around with:
I have done loads of others but they just wouldn't make any sense to you guys so ill spare you!