We’d put your odds at about 1 out of 300,000,000. You’d have a better shot of winning the X-Factor, even if you can’t sing a lick.
Although you may dream of being President, you can't really set out to become President. You can keep it in the back of your mind and conduct yourself in keeping with that aim, but if you make that your life's work you're only setting yourself up for disappointment. Your odds are better of becoming a famous movie star, and that's really saying something.
If you're passionate about politics, be a politician. Change the world from the inside out, in whatever ways that you can. If you climb the ladder, gain some national recognition and the public seems to love you, then maybe it's time to start seriously considering running for the big show. (No, not X-Factor. Nice callback though.)