Gov. Chris Sununu vetoed a bill to shift the state primary day from early September to early August.
Sununu said moving the primary day would conflict with people's summer vacations and lead to reduced turnout.
He added it could make it harder for cities and towns to recruit poll workers and Election Day volunteers.
New Hampshire's September primary is one of the latest in the country. People who support holding it earlier say it would give lesser-known candidates and candidates vying in primaries, more time to compete against incumbents.
Moving the state primary day has long been opposed by the state's top election official, Secretary of State Bill Gardner.
