Montgomery County Executive Douglas M. Duncan yesterday embraced his underdog status in a bid for governor next year, telling several hundred supporters that he had defied expectations before.

Appearing at his annual political picnic, Duncan thanked those who stood by him during his two-decade rise from Rockville City Council member to mayor to his countywide post.

"You know, in each of these races, I was the underdog, written off by many, but not by you," Duncan told the crowd at a Gaithersburg farm. "Over and over, we have beaten the odds."

The crowd, which was treated to ample servings of barbecued chicken and ribs, later broke into applause when Duncan teased his formal announcement, inviting supporters to "think bigger" with him Thursday morning.

Duncan's acknowledgment of the task ahead comes as his opponent in the Democratic primary, Baltimore Mayor Martin O'Malley, is enjoying double-digit leads in early polls.

Citing the gap, some Democrats have started talking anew about the possibility that Duncan step aside to avoid a divisive primary that could leave Gov. Robert L. Ehrlich Jr. (R) in a better position to win reelection. But Duncan, who has seemed on the defensive about the prospect in recent weeks, made light of such talk yesterday.

"Growing up with 12 brothers and sisters, I learned early on you have to fight for what you want and that nothing worth doing is easy," he said to laughter at an event that doubled as a 50th-birthday celebration. There were hayrides and face-painting for the children and strategically placed televisions for diehard Redskins fans.

The $35-a-head event, which benefited from the breezy fall weather and bursts of sunshine, was largely devoid of suspense, as aides had telegraphed Duncan's "pre-announcement" for days.

Duncan seriously considered running for governor in 2002 and has been widely presumed to be a 2006 hopeful since. For months, he has been behaving like a candidate, hiring a campaign manager and spending much of the summer on a tour of all 24 of the state's jurisdictions.

Duncan's revamped political Web site, which debuted over the weekend, already features a "Duncan for Governor" logo and details of Thursday's announcement.

Supporters leaving yesterday's event were offered yellow "Duncan for Governor" bumper stickers, a break with his current blue signage, and directions to Thursday's event in the Rockville neighborhood where Duncan grew up. Aides also spread word of a statewide tour in a recreational vehicle that will continue for five days after Duncan's announcement.

O'Malley, who announced his candidacy last month, welcomed Duncan into the race.

"But we hope he'll shift his focus from making personal attacks on different regions and groups to a positive, issue-oriented campaign about Maryland's future," said Jonathan Epstein, O'Malley's campaign manager, referring to harsh criticism of the mayor's stewardship of Baltimore.

To prevail against O'Malley, most analysts say, Duncan will have to win a commanding majority of votes in his home county and run far ahead of O'Malley elsewhere in the Washington area, particularly in Prince George's County, home to more registered Democrats than any jurisdiction in the state.

Maryland's changing demographics should help Duncan. Since 1986, the last time a Baltimore mayor ascended to governor, the share of Democrats living in the city and surrounding Baltimore County has waned while Montgomery and Prince George's have grown into the state's most Democrat-rich counties.

But O'Malley, who grew up in Montgomery, is hardly ceding the region. He campaigned in Silver Spring on Saturday, attending a "meet and greet" with members of the county's Indian community at a supporter's home.

O'Malley, widely regarded as the more charismatic of the candidates, is also helped significantly by the expansive Baltimore media market, which reaches more than half the state, including most of the Eastern Shore.

Duncan sought to start raising his profile across the state this summer with his 24-jurisidiction "listening-and-learning tour," during which he courted elected officials and party activists and started introducing himself to rank-and-file Democrats.

Sen. Robert J. Garagiola (D-Montgomery), a Duncan booster, said the county executive's efforts should pay off well before votes are cast next September. "He's been somewhat below the radar screen, building his troops," Garagiola said. "He's going to have support in every county across the state. What you're going to see is a groundswell."

In Gaithersburg, Montgomery County Executive Douglas M. Duncan, who hinted that he'll announce his candidacy for governor Thursday, greets supporters at his annual political picnic.