Both Parties Target Voters Who Skip Midterm Elections

Control of the Senate next year depends heavily on the efforts of volunteers such as Karen Bonnewell, a 64-year-old retired nonprofit director who spends a few nights a week calling voters on behalf of Democratic Sen. Kay Hagan.

Using a red marker to color a hand-drawn thermometer, Ms. Bonnewell one recent night tracked the number of calls placed by dozens of volunteers in a cramped office suite here. It is a task familiar in political campaigns, but one taking on unusual importance this fall.

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