Hillary Clinton in Atlantic City, New Jersey. Jessica Kourkounis/Getty Images Democratic presidential frontrunner Hillary Clinton's lead over Donald Trump has narrowed significantly over the past several weeks.

An NBC/SurveyMonkey poll released Tuesday found that Clinton's lead over Trump, the presumptive Republican presidential nominee, had shrunk to just 3 points.

A similar NBC tracking poll released last week showed Clinton with a 5-point lead over Trump among registered voters, down from an 8-point advantage two weeks ago.

Tuesday's release comes after one of Clinton's toughest weeks of the campaign.

Last Monday, FBI Director James Comey criticized Clinton for her email practices as secretary of state. He said that while the FBI would not recommend any charges against Clinton for her use of private email servers, the practices of her and some of her closest associates were "extremely careless."

Tuesday's poll showed that many of Clinton's own supporters were troubled by the finding: 70% of self-described Clinton supporters said her email conduct was "inappropriate."

Still, the poll also noted that it was unclear whether Trump benefited from survey respondents' disapproval of Clinton's email practices. Trump's unfavorable rating remained at 62%, while Clinton's hovered at about 60%, largely unchanged since May.

Clinton also leads Trump in many battleground states, according to recent polls.

A recent set of Ballotpedia polls of swing-state voters showed Clinton leading Trump by significant margins in Florida, Iowa, North Carolina, and Virginia, all states that could help either candidate get closer to winning the 270 electoral college votes needed to clinch the presidency.