Mikie Sherrill entered national midterm politics for the first time Thursday, with her Mission to Deliver PAC announcing endorsements for 13 Democratic candidates with military or national security backgrounds, including Massachusetts Rep. Seth Moulton in his primary challenge against longtime incumbent Sen. Ed Markey. The endorsements mark the first round from Sherrill's PAC, which she launched to support candidates with military service and public leadership experience similar to her own background as a former Navy helicopter pilot and federal prosecutor. Beyond the marquee Massachusetts race, Sherrill's PAC also endorsed Reps. Don Davis of North Carolina and Maggie Goodlander of New Hampshire, both representing competitive districts, with Davis' seat having been redrawn to favor Republicans. Most of the House endorsees are targeting Republican-held seats Democrats hope to flip in November. Markey has countered that ideas matter more than age, saying, "It's not your age, it's the age of your ideas.