Among the 20% who said Obama was born elsewhere, only about half thought there is solid evidence that Obama was born elsewhere, with the other half saying it was only a "suspicion." This would make sense, since the initial question gave only 14% who said another country, with another 6% of leaners then being pushed -- so the latter group would seem the ideal source of people who think Obama was born elsewhere, but also say that they can't prove it.
Furthermore, two-thirds of birthers disapprove of Obama's job performance, with a third actually approving.
The same ABC/WaPo polling sample had Obama's approval rating at 54%, with 44% disapproving. This puts Birther approval of Obama at about 20 points behind the norm. The poll of American adults has a margin of error of Â±3.5%.