Manning declared in Federal Election Commission filings, dated January 5, her statement of candidacy to run as a Democrat in the 2018 election. The paperwork, according to the form, was hand-delivered to the U.S. Senate.
Senator Cardin was elected in 2006 was easily re-elected in 2012, beating his Republican challenger by 30 points in the heavily-Democratic state. Cardin won reelection in 2012 and is now the ranking member of the Senate Foreign Relations Committee.
Former president Barack Obama granted her clemency before leaving office past year.
Cardin's spokesman and the Democratic Party of Maryland declined to comment on Manning's filing. Ben Cardin (D-Md.), who's seen the overwhelmingly favorite as he runs for a third term. His campaign committee has almost $2 million in cash on hand, according to the FEC.
A spokeswoman for Cardin, Sue Walitsky, did not immediately return a phone call.
Conservative news outlet Red Maryland first reported Manning's candidacy.
Manning declined to speak about her filing or to say why she might be running when reached at her home in Bethesda on Saturday. She has also been a columnist on transgender rights and government transparency for The Guardian. He represented the 3rd Congressional District in the U.S. House of Representatives from 1987-2007, when he first entered the Senate, replacing Paul S. Sarbanes, who retired. The general election is November 6. Her candidacy would undoubtedly bring attention, both in Maryland and around the nation, to transgender rights and the rise of the security state.