Heller won despite Obama carrying the state by a 6-point margin. The senator ran slightly ahead of Mitt Romney, while Berkley ran a full 7 points behind Obama, losing votes to the libertarian candidate and Nevada's unique "none of the above" ballot option.

Berkley is facing a House Ethics Committee investigation, and Heller and Republicans relentlessly attacked her for it. In the closing weeks of the campaign, Heller also sought distance from Romney, criticizing him for his "47 percent" remark and promising to work with Reid if reelected.

Heller said on Monday that he "clearly need[s] the Obama voters to win," and picked off just enough of them for his first full Senate term.