9% of Obama supporters defect to Romney: poll

5% of McCain voters have switched to Obama, says Gallup survey

9% of the 2008 supporters of US President, Barack Obama, have now defected to his presidential challenger Mitt Romney, a new poll has said.

"9% of 2008 Obama voters have switched to supporting Romney this year, while 5% of McCain voters have switched to Obama," the Gallup said, revealing the results of its latest surveys.

As many as 86% of voters who say they voted for Obama in 2008 are backing Obama again this year, a smaller proportion than the 92% of 2008 John McCain voters who are supporting 2012 Republican candidate Romney, it said.

The results, Gallup said, are based on July 23-29 Gallup Daily tracking with more than 2,000 registered voters who reported voting in the 2008 election.

Of these, 48% said they voted for Obama and 42% McCain, with the remaining 10% saying they voted for another candidate or not disclosing their vote choice.

However, the 6%-point advantage in reported voting for Obama is similar to the actual seven-point edge he had over McCain in the final 2008 returns, 53% to 46%, it said.

Obama and Romney have been tightly matched so far this year, with the two generally tied or one having a slim one or two point advantage among registered voters in Gallup Daily tracking.