Maryland Lt. Gov. Anthony Brown, left, and Maryland Attorney General Douglas Gansler. (Left: Patrick Semansky/AP; right: Ricky Carioti/The Washington Post)

Two leading Democratic candidates for Maryland governor will launch their television advertising campaigns in coming days, kicking off what is expected to be a multimillion-dollar slugfest ahead of June’s primary.

Despite the bitter tone of the race, Attorney General Douglas F. Gansler and Lt. Gov. Anthony G. Brown plan to debut positive ads, according to previews shared with media outlets on Wednesday.

Gansler’s 60-second spot, which his campaign said will start airing Thursday, recounts his work as attorney general, with Gansler telling viewers that he has fought polluters, big banks and Internet predators, among others.

He also mentions his efforts as Montgomery County’s state’s attorney to bring the so-called Beltway snipers, who terrorized the area in 2002, to justice.

“I take on tough fights and get things done for the people of Maryland,” Gansler says in the ad as images of people he has helped appear on screen.

Brown’s 60-second autobiographical ad touts his work in public service, with a heavy emphasis on his military career, including deployment to Iraq in 2004 as an Army reservist. The ad includes photographs of Brown with his late father, an immigrant from Jamaica.

“Leadership is about inspiring people to achieve goals,” Brown, a former Prince George’s County delegate, says in the ad, which aides said will start running Friday. “To me, that’s public service, and that’s what we can do together.”

The ad war will be a key way for the candidates to define themselves — and their opponents — in a fluid primary that also includes Del. Heather R. Mizeur (D-Montgomery). Mizeur’s campaign did not announce any immediate plans for the airwaves.

A Washington Post poll last month showed Brown leading his rivals by a substantial margin. But more than four in 10 Democrats and Democrat-leaning independents said they were undecided. And almost six in 10 who had a preferred candidate said there was at least some chance they could switch allegiances before the June 24 primary.

Gansler’s campaign said his first ad will air in both the Washington and Baltimore media markets. Traditionally, candidates have launched ads first in Baltimore, where television time is significantly less costly than in Washington.

The campaign plans to spend about $200,000 on the initial ad buy, a Gansler adviser said.

Justin Schall, Brown’s campaign manager, would not say whether Brown plans to air ads in both Baltimore and Washington. He said that the campaign is spending more than $100,000 on the initial buy.

Brown and Gansler both have plenty to spend between now and June. In reports released in January, Brown and his running mate, Howard County Executive Ken Ulman, said they had about $7.1 million in the bank, while Gansler and his running mate, Del. Jolene Ivey (D-Prince George’s) said they have about $6.3 million.

Mizeur reported having about $750,000 on hand.

None of the Republicans running for governor reported fundraising totals in January that would enable them to run sustained television advertising campaigns. One of them, Harford County Executive David R. Craig (R), launched a 30-second radio ad on several Baltimore area stations last week.