Former Maryland Gov. Martin O'Malley said Tuesday he will not seek the Senate seat of retiring Sen. Barbara Mikulski, keeping open his option of running for president in a Democratic primary likely to include Hillary Rodham Clinton. 

O'Malley said in a statement he was "hopeful and confident that very capable public servants with a desire to serve in the Senate will step up as candidates for this important office. I will not be one of them." 

Mikulski announced plans to retire on Monday, giving O'Malley an alternate path if he wanted to avoid what looks today to be a longshot bid against Clinton. 

Little known outside his home state, O'Malley has yet to gain much traction in a hypothetical matchup against Clinton, who has a network of super PACs already working on her behalf and much of the party's establishment eagerly waiting for her to announce her candidacy. Those pining for someone other than Clinton have largely focused their longing not on O'Malley, but Massachusetts Sen. Elizabeth Warren -- who tells everyone who asks she isn't running. 

O'Malley has deep ties to Mikulski. While in law school, he served as field director on her first Senate campaign in 1986, and his mother Barbara has worked as a receptionist in Mikulski's Washington office since 1987. Yet the retiring senator has already endorsed Clinton for 2016.