Maryland Del. Heather R. Mizeur turned her attention Thursday to a popular topic for Democratic gubernatorial hopefuls — expanding access to pre-kindergarten education — and put forward a more ambitious plan than her rivals.

During a news conference in Baltimore, Mizeur (Montgomery) laid out a phased-in approach that would offer full-day pre-K programs to 4-year-olds across the state. She would also ensure half-day programs are eventually available to all 3-year-olds in lower-income families.

The cost of Mizeur’s initiative, when fully phased in, would be close to $280 million a year, according to estimates released by her campaign. She declined to say how the state would pay for it.

“Being governor is about setting priorities,” Mizeur said as she stood on the playground at Downtown Baltimore Child Care. “These programs will be funded.”

Mizeur faces two better-known and better-financed rivals in the June Democratic primary: Lt. Gov. Anthony G. Brown and Attorney General Douglas F. Gansler, who’ve both offered their own pre-K proposals in recent weeks.

On Thursday, Mizeur also proposed a major expansion of state child-care subsidies for low-income families, as well as funding for additional after-school and summer programs for those in kindergarten through eighth grade.

The estimated costs of those initiatives, once phased in, would be $95 million a year and $73 million a year, respectively.

In their plans, Brown and Gansler both aim to phase in full-day pre-K to all interested families with 4-year-olds. Brown says his plan would be fully implemented by 2022.

Gansler and Brown have also said they would help pay for their plans with proceeds from Maryland’s casinos.

Mizeur rejected that approach Thursday, saying the programs shouldn’t be dependent on gambling, which takes money from the kind of low- and middle-income families she is trying to help.