The state has not elected a Republican to the Senate since 2010. But Chris Pappas, the likely Democratic nominee, anticipates a tough race against a well-known opponent, John E. Sununu.

PLYMOUTH, N.H. — Chris Pappas has been seen as Democrats’ presumed Senate nominee in New Hampshire since he entered the race more than a year ago. And for most of that time, the…

The state has not elected a Republican to the Senate since 2010. But Chris Pappas, the likely Democratic nominee, anticipates a tough race against a well-known opponent, John E.…