Martin O'Malley plans to announce his presidential intentions on May 30 in Baltimore, CBS News confirms.
An O'Malley aide says the former Maryland governor will hold a conference call with supporters on Thursday night to discuss his plans. The aide spoke on condition of anonymity to discuss internal planning and was not authorized to speak publicly.
O'Malley has been considering a potential challenge to Clinton, the leading Democratic contender, for months and courted voters in New Hampshire on Wednesday.
The former Maryland governor has made headlines recently with his public responses to the violence in Baltimore, where he had previously served as the city's mayor. After the death of Freddie Gray, a 25-year-old black man in police custody, O'Malley made appearances in the beleaguered city.
"I did not dedicate my life to making Baltimore a safer and more just place because it was easy," O'Malley said in early Mayon NBC's Meet the Press, adding that he's "more deeply motivated now to address what's wrong with our country and what needs to be healed and what needs to be fixed... There are people in whole parts of our cities who are being totally left behind and disregarded. They are unheard."
If O'Malley announces a bid for the White House, he will be the second major player to challenge the former secretary of state. Sen. Bernie Sanders, I-Vermont, has also said he will seek the Democratic nomination.
O'Malley's plans were first reported by The Washington Post.