Heitkamp has proven to be a strong campaigner so far and has been neck-and-neck with Rep. Rick Berg (R-N.D.) in recent polling.

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The ad reservation brings the DSCC's total fall reservations to $21.5 million, including a $5.1 million investment in Ohio placed Tuesday, $7.5 million in Virginia, $4.5 million in Missouri and $3.2 million in Montana.