The open U.S. Senate seat in New Hampshire, following Jeanne Shaheen’s retirement, has intensified competition between likely Democratic nominee Chris Pappas and Republican contenders including John Sununu, with national control of the chamber at stake. This dynamic, combined with New Hampshire’s large pool of undeclared voters and history of elevated midterm participation, keeps turnout forecasts closely clustered across ranges. Primary elections on September 8 and the November 3 general remain the key near-term catalysts, as party mobilization efforts, candidate visibility, and broader voter enthusiasm levels could shift participation higher or lower depending on campaign intensity and external events.