Incumbent Republican governor Bob Ehrlich ran for a second term, but was defeated by the Democratic nominee, Baltimore Mayor Martin O'Malley.

Baltimore Mayor Martin O'Malley and Montgomery County Executive Doug Duncan emerged as the two Democratic candidates for governor in late 2005.

O'Malley selected Anthony Brown, a black State Delegate from Prince George's County and a veteran of the Iraq War, as his running mate.

[9] The Washington Post and The Washington Times both endorsed Ehrlich in his bid for re-election, with the Times praising Ehrlich's "brand of moderate conservatism that offers a refreshing contrast" to the state's historically Democratic leanings[10] and the Post called him "a generally proficient, pragmatic governor" and praised him for "successes on transportation, the environment and education.

"[11] In turn, The Baltimore Sun endorsed O'Malley, saying, "the progress under the mayor's tenure is clear and irrefutable", and that he addressed "rising crime, failing schools and shrinking economic prospects.