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PHILADELPHIA (CBS) — With the 2018 midterm elections just weeks away, Pennsylvania’s Democratic Sen. Bob Casey and Republican challenger Congressman Lou Barletta held their first debate in an effort to sway voters before they head to the polls.

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The candidates took to the stage in Philadelphia to tackles topics such as health care, the opioid epidemic, and the economy.

During the debate, Barletta accused the Casey campaign of a low blow. Sen. Casey’s camp has been airing a commercial accusing Barletta of voting to let insurers strip coverage for pre-existing conditions.

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The ad features a young twin child fighting cancer. Barletta says his grandson, a twin, was diagnosed with cancer in September.

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The ad has since been pulled from the airwaves in northeastern Pennsylvania.

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Election day is Nov. 6.