Senator Kamala Harris of California, the former prosecutor who is running for the Democratic presidential nomination, on Monday committed to a host of executive actions to implement gun control measures that have long failed to pass in Congress.

At a town hall hosted by CNN, Ms. Harris said that, if elected, she would sign an executive order mandating background checks for customers of any firearms dealer who sells more than five guns a year. The executive actions would also include more strident regulation of gun manufacturers that could result in revoked licenses or prosecution, as well as an attempt to close the loophole that allows some domestic abusers to purchase guns if their victim is an unwedded partner.

[Five Democrats took questions from college students on CNN. Here are the highlights.]

“There are people in Washington, D.C., supposed leaders,” Ms. Harris said on CNN Monday evening, “who have failed to have the courage to reject a false choice which suggests you’re either in favor of the second amendment or you want to take everyone’s guns away.”

“We need reasonable gun safety laws in this country, starting with universal background checks and a renewal of the assault weapon ban,” she added, “but they have failed to have the courage to act.”

She said she would introduce the executive actions if Congress did not pass gun control legilslation in the first 100 days of her presidency.

The announcement marks the second policy proposal of Ms. Harris’s presidential run; the first was a federal increase in teacher pay. The two policies dovetail with Ms. Harris’s political wager, which combines her historic status as one of the most viable black women to run for president with a patchwork of incrementally progressive proposals.

In the past year, gun control has re-emerged as a top priority for Democrats, particularly after the youth-led March for Our Lives brought thousands of motivated high schoolers to Washington last year. Even as the issue has gained traction in statehouses, however, Congress has failed to enact any major gun control legislation, and Ms. Harris’s executive action would be undoubtedly controversial and would quite likely face legal challenges.

After the shooting of elementary school students in Newtown, Conn., former President Barack Obama made gun control a top priority, exerting significant political capital in a failed attempt to pass universal background checks for gun purchasers.

As a California prosecutor, Ms. Harris supported such legislation, while also calling for bans on assault weapons and high-capacity magazines, prohibiting those convicted of a federal hate crime from purchasing guns, and making gun trafficking a federal crime.