DONALD Trump's presidential prospects are disintegrating as questions about President Barack Obama's birth certificate fade, a new poll showed overnight.
Mr Trump plummeted from the head of the Republican primary field to fifth-place, tied with long-shot Republican Ron Paul of Texas, according to a newly-released survey from Democratic-aligned firm Public Policy Polling (PPP).
The 64-year old Mr Trump, who has not yet said whether he will run for the Oval Office, had the support of 8 per cent of Republicans, compared to 26 per cent just one month earlier.
But that was before Mr Obama released his long form birth certificate to satisfy any lingering questions about his lineage and cut off speculation among some Republican voters about his eligibility for president.
Mr Trump was virtually the only potential contender to champion that point of view, having gone so far as to allegedly send personal investigators to Mr Obama's birthplace of Hawaii.
In the poll, 34 per cent of Republicans said they were not sure that Mr Obama was born in the US, down from 51 per cent in a February survey, PPP said.
Mr Trump's fall was a boon for former Arkansas Governor Mike Huckabee and former Massachusetts Governor Mitt Romney, who led the GOP field with 19 per cent and 18 per cent, respectively. The result was in line with polls from various organisations taken before Mr Trump's near-instantaneous rise over the past two months.
Mr Romney, who also ran unsuccessfully for the nomination in 2008, recently announced the formation of a presidential exploratory committee. Mr Huckabee, has been more cryptic when it comes to his thought process about a potential run.
The PPP survey was an automated telephone poll of 610 usual Republican primary voters and had a margin of error of 4 percentage points.