Democratic presidential candidate Hillary Rodham Clinton speaks to the Human Rights Campaign in Washington. (Jose Luis Magana/AP)

Democratic presidential candidate Hillary Rodham Clinton is pledging tighter controls on the sale of firearms at gun shows if she is elected, and she says she would go around Congress if necessary.

On Monday, Clinton plans to propose to take executive action to crack down on high-volume gun sellers at gun shows, where rules differ from those at bricks-and-mortar stores. Clinton said that if she is elected, she will require that anyone attempting to sell a significant number of guns be deemed “in the business” of selling firearms.

Her campaign said that designation would ensure that high-volume gun sellers are covered by the same rules that apply to gun stores, including requiring background checks on gun sales. Clinton plans to announce aspects of her proposed gun policy Monday at appearances in New Hampshire, an important early-voting state with rural traditions and a mixed outlook on additional federal gun control.

As a candidate, Clinton has been passionate and blunt about gun violence and the lack of congressional action to limit firearm sales or pass other gun-control measures.

“We can’t wait any longer to act on gun violence prevention,” Clinton said Sunday via Twitter. “Every time there’s another massacre, Republicans say ‘now is not the time to talk about guns,’ ” she wrote. “Yes, it is. But more than talk, it is time to act.”

Handguns on display at the Nation's Gun Show at the Dulles Expo Center in Chantilly, Va., on Oct. 3. (Jabin Botsford/The Washington Post)

Clinton and her close competitor for the Democratic nomination, Sen. Bernie Sanders (I-Vt.), have endorsed tighter gun control in response to last week’s massacre at an Oregon community college. Clinton’s campaign said she would vow to use executive authority to circumvent Congress if it did not act on what she calls “common sense” measures.

She plans to outline those proposals at two town-hall-style events Monday, her campaign said Sunday. She supports changes to make the federal background-check system more comprehensive and to limit the ownership of military-style assault weapons.

Gun shows are a frequent complaint of gun-control advocates, along with online firearm sales that can go around the regular background-check system. The Republican-led Congress has resisted new regulation, leading President Obama to use his executive authority in 2013 to subject gun purchases by corporations and trusts to background checks and ban almost all reimports of military surplus firearms to private entities.