"It's time we have somebody to fight for us, someone who doesn't embarrass us, someone who doesn't get kicked off his committee. We need mature, responsible leadership," she said.
Democratic leaders removed Mooney from the Senate Judicial Proceedings Committee last year after he refused to help them block death penalty moratorium legislation.
Mooney has said he makes no apologies for going against the majority in order to represent his constituents' conservative views. He is characterizing the choice for voters as liberal versus conservative.
During her whirlwind announcement tour, Hecht portrayed herself as an experienced and proven leader in contrast to Mooney, who has butted heads with the establishment since he came to the Senate four years ago.
In two terms in the House of Delegates, Hecht has served on the House Appropriations Committee, where she is vice chair of the transportation and environment subcommittee.
Hecht, 54, touted her accomplishments during the legislative session that just ended - strengthening laws against sex offenders, helping state employees and establishing tax credits for businesses that encourage their employees to work from home.
"I don't know if it's liberal or conservative, but it's the right thing to do," she said.
Sharpsburg Mayor Sid Gale met Hecht for the first time Thursday, shortly before he introduced her to residents of the town of Sharpsburg, with a population of about 800.
"She's been a strong supporter of Washington County issues in the past. We're glad to welcome her here to Sharpsburg and hear what she has to say," he said.
Gale admitted he was disappointed when the town was drawn into a legislative district that is dominated by Frederick County voters instead of Washington County voters.
But Gale said he agreed to back Hecht when asked by her campaign.
Even though Gale is a Democrat, it wasn't an automatic decision. He and many Sharpsburg voters are known for their political independence, he said.
"I think she is obviously a strong supporter of issues that are important to us," he said, citing agricultural land preservation.
Hecht was flanked by her husband, Robert Forder, who wore a name pin that identified him as "Sue Hecht's husband."
Among the crowd were several union representatives, including Glenard Middleton, the state director of the American Federation of State, County and Municipal Employees, who gave up a chance to meet the University of Maryland's national champion basketball team to be at Hecht's announcement.
Hagerstown Mayor William M. Breichner, a Democrat, also was in Sharpsburg.
Breichner said Hecht has backed Hagerstown's effort to get the University System of Maryland Hagerstown Education Center even though the city is not within the boundaries of her delegate district, which runs from the city of Frederick west to encompass Smithsburg and Ringgold in northeastern Washington county.
Hecht started the day in Frederick, making her announcement to supporters who included John W. Derr, the Republican senator Mooney ousted four years ago.
Derr said he likes Hecht, but admitted that part of his reason for backing her was lingering resentment of Mooney for running what he called a "negative and vicious" campaign.
"It sounds like sour grapes and maybe it is. There's a little bit of anger there," he said.
After her announcement in Frederick, Hecht boarded a school bus with about 40 of her followers.
The bus cut a swath through the district, stopping in Brunswick, Sharpsburg and at five Frederick County assisted living centers.
The nursing home visits were designed to highlight her advocacy for senior citizens. Hecht has received national attention for her work on video cameras to guard against elderly abuse.
Hecht wrapped up her tour with a Jamboree at the Independent Hose Co. in Frederick, Md., where she was endorsed by Baltimore Mayor Martin O'Malley.
In District 3 as redrawn by Gov. Parris Glendening, Republicans hold a slight majority over Democrats, but there are large number of independents, said Sue Tuckwell, Hecht's campaign manager.
It's expected to be an expensive campaign. As of November, Mooney had $177,733 in his campaign account to Hecht's $94,934, according to the State Board of Elections.