Manning, 30, is running as a Democrat, which means she would challenge Sen. Ben Cardin in his primary race.
Manning was sent to prison after a 2013 espionage conviction for leaking classified documents to Wikileaks. She was sentenced to 35 years, but President Barack Obama commuted the sentence at the end of his term.
Manning, formerly known as Bradley Manning, was a private in the U.S. Army when she leaked the documents. Manning filed her candidacy Thursday with the Federal Election Commission. Her candidacy was first reported by The Washington Post.
Cardin is currently serving his third term and is up for re-election in November. While Manning is originally from Oklahoma, Cardin has deep ties in Maryland, where he served in the Maryland House of Delegates for 20 years before taking the seat of retired Sen. Paul Sarbanes, according to the Baltimore Sun. His campaign war chest already boasts upwards of $2 million.
Manning was arrested in 2010 after she gave Wikileaks almost 75,000 documents related to the war efforts in the Middle East and information about Guantanamo Bay prisoners. Usually outspoken on social media, the whistle-blower has not commented on her possible entry into the political arena.
President Trump has been critical of Manning, once referring to her as an “ungrateful traitor.”