Story highlights New Hampshire's race is one of several that could decide control of the US Senate

Ayotte has wavered in her support of Trump, who is plunging in the polls

Washington (CNN) A new poll of the New Hampshire Senate race finds Democratic nominee Maggie Hassan, the state's governor, taking a strong lead against sitting Republican Sen. Kelly Ayotte.

The WMUR poll released Thursday showed 46% of likely voters supported Hassan, 38% for Ayotte, 3% for someone else and 13% undecided. The poll showed Hassan leading among undecided voters as well.

Earlier this week, WMUR released its survey of the presidential race, showing Hillary Clinton leading Donald Trump by 15 points -- a much stronger lead for the Democratic nominee than other polls had found in recent weeks.

The swing-state race is one of several close contests around the county that could decide control of the US Senate, and Ayotte's re-election bid has been complicated further by her party's controversial presidential nominee.

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