"Oh, yeah, I think everybody knows that," Gansler said after a candidate's forum in Silver Spring.
Gansler told the crowd that the contest for governor "isn't a sixth grade class election."
When asked to clarify that remark afterward, Gansler said a governor needs to have executive experience, such as his own in running the state's attorney office in Montgomery County and running the attorney general's office.
"This is a real job, and it requires real leadership and credibility," Gansler said. "What I'm suggesting is, of the Democratic candidates, I'm the only one with executive experience. I'm the only one in the race that's credible because I get things done. ... I'm not just voting on something or watching from the sidelines. I'm getting things done."
Ulman, who is term-limited, considered his own bid for governor and raised $2.1 million to finance it before agreeing to join Brown's ticket last spring.
Brown's campaign manager, Justin Schall, said in a statement that Brown has been a leader as lieutenant governor, as an colonel in the Iraq war and as Majority Whip in the House of Delegates.
"To suggest that these experiences do not qualify him for governor is ridiculous. The people of Maryland deserve a better debate than this," Schall said.
Del. Heather Mizeur, a two-term delegate from Montgomery County, is also in the Democratic contest. She has worked as a policy director for former Sen. John Kerry and owns a health care and energy policy consulting company called The Mizeur Group.
In an interview, Gansler said that under some circumstances, a lieutenant governor could be better qualified to be a governor that a county executive, but as a general rule being a county executive is better training to be a manager.
Gansler went on to attack two projects overseen by Brown - the rollout of the health exchange and preparing the state for an influx of jobs from the military Base Realignment and Closure process - as "both woeful disasters." Because of that, Gansler said, Ulman would have better experience to better governor than Brown.
"Is this particular county executive more qualified than the lieutenant governor? Of course," Gansler said.