Washington (CNN) Vermont Sen. Bernie Sanders has opened up a 9-point lead over Hillary Clinton in New Hampshire and is closing ground on the Democratic front-runner in Iowa, according to an NBC News/Marist poll released Sunday.

Sanders is leading Clinton 41-32, up a whopping 19 points from a similar poll in July. And Clinton's support dropped by 11% in Iowa over the same time.

Clinton has been plagued by continued questions over her use of private email while at the State Department, contributing to voters' lack of trust in her. Though she leads Sanders in national polling, the "drip, drip, drip" nature of both congressional and federal inquiries into her email practices are having an effect on her candidacy.

Vice President Joe Biden, who has been publicly mulling a run, has been staying steady at 12% support in New Hampshire and 16% in Iowa.

The poll also shows Republican front-runner Donald Trump maintaining commanding leads in both of the early nominating states -- 29% in Iowa and 28% in New Hampshire.