Presumptive Republican presidential nominee Mitt Romney has opened up a 1-point lead in the key battleground state of Wisconsin, according to a poll released Tuesday.

The poll by Democratic-leaning Public Policy Polling shows Mr. Romney leading President Obama 48 percent to 47 percent in the Badger State. The results are identical to those from a Rasmussen Reports poll released last week.

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Mr. Obama, who won Wisconsin by 14 percentage points in 2008, consistently has led in state polls but has seen his lead evaporate in the two weeks since Mr. Romney announced Wisconsin GOP Rep. Paul Ryan as his running mate.

The poll showed that Republican voters have rallied behind the Romney-Ryan ticket, with 93 percent saying they will vote Republican, and that Wisconsin independents have shifted away from the president, who holds just a 4-point lead with them after enjoying a 14-point lead last month.