(CNN) - President Barack Obama's advantage over his Republican challenger in Pennsylvania is now at eight points which is right on the edge of the sampling error, according to a new poll.
Mitt Romney, however, won last Wednesday's debate by a wide margin, the survey shows.
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The Philadelphia Inquirer/Susquehanna Bank Poll released Thursday found Obama at 50% and Romney at 42%. The same outlet's poll found Obama with an 11 point lead following the party conventions. The survey was conducted October 4-8, in the days immediately following the first debate between Obama and Romney last week.
A poll released on Tuesday by Siena College found the race significantly closer: 43% for Obama, 40% for Romney. That survey was conducted partly before and partly after last week's debate.
A CNN Poll of Polls assembled on September 28, shortly before the debate, found the incumbent ten points over his challenger.
Just under two out of three likely voters in Pennsylvania (65%) thought Romney won that debate, while only 15% said Obama won. Vice President Joe Biden and GOP candidate Paul Ryan face off on Thursday night.
One in three voters said they were more likely to support Romney as a result of the first debate.
Pennsylvania is marked as leaning in Obama's direction this year on the CNN Electoral Map.
Obama won by 10 points in 2008, and Sen. John Kerry, also a Democrat, won by 3 points in 2004.
This poll included 600 likely voters in Pennsylvania and was conducted from October 4 to 8.
– CNN's Paul Steinhauser and Gregory Wallace contributed to this report