The seat Manning is vying for is now held by Democrat Ben Cardin, who has held it since 2007. Cardin's seat is up for re-election in November; Cardin has served two terms in the U.S. Senate representing Maryland.
The election document lists Manning's address as that of a luxury apartment tower in North Bethesda. She is running as a Democrat.
Manning has long maintained that she leaked the documents in order to spark public debate.
Formerly a U.S. Army soldier assigned to be an intelligence analyst for the U.S. Department of Defense, Manning leaked classified military documents to WikiLeaks.
Manning came out publicly as transgender in 2013, shortly after being convicted on 20 charges including violations of the Espionage Act, theft and computer fraud.
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In his statement, Obama said that Manning's sentence was "disproportionate" to those faced by other whistleblowers.
At the time she said she wanted to expose what she considered to be the US military's disregard for how the Iraq War was affecting civilians. In July, she dissented Trump's choice to forbid transgender individuals from the military at a rally at the White House. She was placed in solitary confinement after attempting suicide twice.
Manning could not immediately be reached for comment.
"Police and prosecutors steal more through "civil asset forfeiture" than all "property crime" combined", Manning wrote.