Fine. So you can't back it up. Why don't you just admit it? Your figures are wrong.
In Aug, 2001, the Gallup poll showed that 17% of Americans thought that abortion should be illegal under all circumstances, and 43% thought it should be illegal except for a few circumstances. That adds up to 60% of Americans who think that abortion should be illegal under most or all circumstances.
You can find that poll at:
http://www.gallup.com/poll/topics/abortion.asp