Story highlights 4 percent of voters remain undecided, the poll found

Clinton leads in the state's "generally decisive" I-4 corridor

(CNN) Hillary Clinton has single-digit leads over Donald Trump in Florida and New Hampshire, according to a new polls conducted after the first presidential debate.

A Mason-Dixon poll of likely voters in Florida found Clinton leading Trump 46% to 42%, just outside of the poll's margin of error. Libertarian candidate Gary Johnson drew 7% support, ahead of Green Party candidate Jill Stein at 1%. Four percent said they remain undecided.

Clinton's edge in the state is powered by her support among women and nonwhite voters, and she performs better with Democrats (83%) than Trump does with Republicans (77%). Trump is buoyed by strong support among men and white voters.

The poll also broke down each candidate's support by geography, which showed Clinton with an advantage over Trump in the southeast portion of the state, where she leads 58% to 29%. Trump was strongest in the state's southwest, leading there 51% to 36%.

But in the "generally decisive" I-4 corridor, according to the poll, Clinton has a key advantage. She is leading 47% to 40% in the Tampa Bay region, which the Mason-Dixon poll identifies as a "swing area," while Trump's advantage in Republican-leaning central Florida is a slim 46% to 43%.

Read More