"The presidency of the United States is not some crown to be passed between two families," the former Maryland governor told ABC's "This Week."
O'Malley spoke as former Secretary of State Hillary Rodham Clinton is considered a likely candidate and clear front runner for the Democratic nomination. Former Florida Gov. Jeb Bush is considered a probable contender for the Republican nomination.
O'Malley said he will decide whether to run for president this spring and questioned whether his party's nomination of Clinton — also a former senator and first lady — is inevitable.
"History is full of times when the inevitable front-runner is inevitable right up until he or she is no longer inevitable," he said.
O'Malley's response to questions slowed noticeably when asked what he considers the top foreign threat faced by the U.S.