Brooks beat former federal prosecutor Ryan Crosswell, former Northampton County executive Lamont McClure and former legislative aide Carol Obando-Derstine.
Brooks has excited supporters with his blue-collar bona fides and the chance for him to galvanize working-class Pennsylvanians to support him. He was also endorsed early on by Pennsylvania Gov. Josh Shapiro and has support from national Democrats.
However, Brooks has faced scrutiny from both Democrats and Republicans over how he appeared to get so much insider support - including from Shapiro - before the primary, as well as details about him, such as his stock trades that appear to clash with his 'everyman' image.
Brooks faced three other candidates, including former federal prosecutor Ryan Crosswell, in the primary.
What it means for midterms
The 7th district in Pennsylvania, which includes the Lehigh Valley, is among the most competitive in the country, and it's one of the four congressional districts in Pennsylvania that Democrats are targeting in the midterms.
Mackenzie himself only won and flipped the district in 2024 by around one percentage point in a district that President Donald Trump carried by around 8 points. In a midterm year that may favor Democrats, Brooks has a chance at flipping the seat, although Republicans have already been indicating they plan to work hard to defend it and keep it in Republican control.
ABC News contributed to this report.