This video may be a metaphor of Obama; how one individual can topple an entire nation.
[youtube]http://www.youtube.com/watch?v=y97rBdSYbkg&hd=1[/youtube]
A domino can knock over another domino about 50% larger than itself. A chain of dominos of increasing size makes a kind of mechanical chain reaction that starts with a tiny push and knocks down an impressively large domino.