LITTLETON, N.H. — With the Tea Party wind at their backs two years ago, voters here swung crimson. They expelled a rash of newly installed Democrats and elected two Republican congressmen, a Republican senator, and Republican super-majorities in both legislative houses.

But this election, like the rest of the country, New Hampshire appears split down the middle, with the top elective slots considered among the most competitive nationwide, fueled by out-of-state money and aggres­sive campaigns.