[5] In 2011, Horn founded the conservative non-profit organization We the People: A First in the Nation Freedom Forum, which she terminated following her election as Chairman of the NH GOP.

[6] The organization sponsored town hall type meetings through New Hampshire in the lead-up to the state's first-in-the-nation primary.

[8] Horn won the state GOP chairmanship on January 26, 2013, defeating Andrew Hemingway in an election to replace the outgoing chairman, Wayne MacDonald.

Senator Kelly Ayotte and outgoing congressmen Frank Guinta and Charlie Bass,[11] along with 40 other elected officials.

Both Horn and her opponent Hemingway had characterized the release of the information by fellow Republican Joe Barton as a "personal attack" that had no place in the election.

[20] Horn contends that voting by out-of-state Democratic volunteers, including the niece of Vice President Joseph Biden, in New Hampshire elections is illegal and constitutes voter fraud.

Along with several other prominent Republican strategists, she co-founded the Lincoln Project, which aimed to defeat Trump and his supporters in Congress.

[25][26] On February 5, 2021, she announced that she was resigning from the Lincoln Project, citing fellow co-founder John Weaver's history of sexual misconduct against young men.