Elizabeth Mitchell tries futilely to end the Purge in Universal’s new trailer for “The Purge: Election Year.”

The trailer opens with a bit of seriously dark humor — testimonials from Middle America with gorgeous scenes of the heartland and sincere assertions, such as, “I purge because it’s my civic duty.”

The Purge, now in its third iteration as a movie, is a 12-hour period during which all crime is legal. Mitchell’s senator character, Charlie Roan, is running on a pledge to end the purge, but gets betrayed by enemies within the government — leaving it up to the heroic Leo (Frank Grillo) and other new allies to help keep her alive.

“What you doing outside on Purge night, senator?” a civilian asks amid the chaos.

The second installment, “The Purge: Anarchy,” took in $108 million worldwide. Jason Blum is producing again along with Sebastien Lemercier and Platinum Dunes partners Michael Bay, Brad Fuller and Andrew Form.

“The Purge” was Blumhouse’s first production in 2013 under its first-look deal with Universal. The sci-fi thriller, starring Ethan Hawke and Lena Headey, became a major success, earning $89 million globally on a $3 million budget.

“The Purge: Election Year” opens on July 1 — perhaps the most patriotic weekend of the year.