(CNN) – Among a slate of battleground state polls showing a tightening race between Mitt Romney and President Barack Obama is a survey in Pennsylvania, where Obama, until recently, held a lead over his rival but is now statistically tied with the GOP nominee.
The poll, from Siena College, showed Obama with the backing of 43% of likely Pennsylvania voters, compared to 40% who backed Romney. That's within the 4.2% sampling error. Another 12% of likely Pennsylvania voters in the Siena poll remained undecided. The survey was conducted October 1-5, partially before and partially after the first presidential debate between Obama and Romney, which took place October 3.
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The latest poll showing a close race between Obama and Romney in Pennsylvania is a shift from the end of September, when a CNN Poll of Polls in the state showed Obama with a 10-point advantage over Romney. The Poll of Polls averaged five Pennsylvania polls of likely voters over a two and a half week period.
CNN's Electoral Map rates the state as leaning towards Obama. The president carried Pennsylvania in 2008 by 10.3%. There are 20 electoral votes at stake in November.
At a rally in Pennsylvania on September 28, Romney opened by saying a win in the state would amount to a surprising defeat for the president.
"You know we really would shock people if early in the evening of Nov. 6 it looked like Pennsylvania was going to come our way and actually did come our way," Romney said at the Union League Club. "That could happen. That could happen."
On Tuesday, the Romney campaign said they were shifting five of their 64 Pennsylvania staffers to Ohio, where early voting is already underway.
"We have so much going on in Ohio that we're temporarily asking some staff to help out," a Romney campaign official said.
The Siena Poll of Pennsylvania was conducted by telephone from 545 likely Pennsylvania voters between October 1 and October 5. The sampling error was plus or minus 4.2 percentage points.
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