After attending a Lenten church service, Duncan plans a news conference with anti-slots black ministers, and he said he intends to contrast his strong opposition with what he calls O'Malley's philosophical inconsistency on the issue.
"What I don't understand is how someone like Marty O'Malley can stand up and say, 'Slots are morally bankrupt, but I'm going to do everything I can to get them here in the state of Maryland,'" Duncan said. "That's an irresponsible position."
O'Malley has said he thinks slots are a poor way to fund annual education expenses but that he doesn't object to a limited expansion of gambling at racetracks.
"The mayor thinks a reasonable, responsible compromise is possible to protect thousands of jobs in the horse racing industry, keep the Preakness in Baltimore and use some funds for school construction," said O'Malley spokesman Stephen Kearney. "After three years of gridlock, it's time to move on to other issues facing the state."
Duncan has used anti-slots rallies to contrast his position with that of Gov. Robert L. Ehrlich Jr., who strongly backs expanded gambling. But today's event marks his most high-profile effort yet to make slots an issue for the primary.
It's a wise move, said Ronald Walters, a political science professor at the University of Maryland. Duncan is behind in the polls, and one way to make up the difference is to attack O'Malley on slots, he said.
"I don't think O'Malley can afford, regardless of what the polls say, to have a split in his African-American base," Walters said.
The Rev. Grady Yeargin of Baltimore's City Temple Baptist Church said he believes that many in his congregation and community agree with Duncan.
"This is another way for poor people to be poorer," said Yeargin, who is host to the multidenominational Lenten services today.
Delegates from Prince George's County and Baltimore voted overwhelmingly this month to oppose slot machines in their jurisdictions. Those two jurisdictions, plus Duncan's home county, made up 53 percent of the vote in the 2002 Democratic primary.
But a strategy of opposing slots is not without pitfalls for Duncan.
Some black ministers have endorsed slots for their economic development potential, and there are sizable numbers of more conservative Democratic primary voters in Anne Arundel and Baltimore counties, where slots are popular and where Ehrlich won by large margins in 2002.
The Maryland-D.C. chapter of the AFL-CIO favors slots at the tracks to create jobs, and leaders in some member unions said they are bothered by Duncan's anti-slots rhetoric.
Duncan said the focus should be on creating high-tech jobs, not gambling.
"While we've been debating gambling, we've slipped from third-best in biotech to the fourth-best," he said.
Roxie Herbekian, associate director for the Mid-Atlantic Region of Unite Here, a hotel and restaurant workers union with 5,000 members in Maryland, said she was "taken aback" that Duncan would downplay the job implications.
"Lots of people want to work as cooks and waiters and waitresses and bartenders, and take care of their families," she said.
Senate President Thomas V. Mike Miller said slots opposition may attract some Democratic primary voters, but it's a general election loser.
"You go into areas where you still have blue-collar Democrats and independents, it is a winning issue," Miller said. "They did vote for Ehrlich, and if you are going to take those votes away from him, you need to take the issue away from him as well."