Baltimore Mayor Martin O'Malley, a Democrat who has long eyed a move to Annapolis, told supporters last night that he will announce his 2006 bid for governor next week.

O'Malley shared plans for his Sept. 28 announcement during a conference call with more than 100 supporters, according to participants. The evening event in Baltimore will bring to a close an extended period during which O'Malley has said repeatedly -- and often playfully -- that he is "laying the groundwork" for a campaign without revealing his true intentions.

"He announced the announcement," said Arnie Gordon, an O'Malley district coordinator in Montgomery County who took part in the call. "I felt very, very optimistic. We've always felt this is the guy in the best position to beat Bob Ehrlich."

Although O'Malley's decision to challenge Gov. Robert L. Ehrlich Jr. (R) was widely expected, his announcement next week will come earlier in the political cycle than many observers had expected, bringing the race into sharper focus and putting a spotlight on Montgomery County Executive Douglas M. Duncan, who has also pledged to seek the Democratic nomination next year.

Jody Couser, a spokeswoman for Duncan's as-yet-unannounced campaign, said Duncan will trumpet his plans to run for governor by the end of October.

"Absolutely he's committed to going forward, and you'll see an announcement from him in coming weeks," said Couser, whose boss spent much of the summer on a county-by-county "listening and learning" tour and has hardly been coy about his intentions.

O'Malley, who was reelected to a second term as mayor last year with 87 percent of the vote, has touted Baltimore's "comeback" during recent appearances throughout the state. He points to a drop in the city's overall crime rate, rising test scores among younger children and renewed business and residential investments in Baltimore. In April, Time magazine named O'Malley of one of the country's five best big-city mayors.

But stewardship of a big city also provides O'Malley with some baggage as he ramps up for higher office. The city's homicide rate, though down since O'Malley took office in 1999, has not dropped as rapidly as he promised and remains higher than many municipalities of comparable size. And other big-city mayors who have sought higher office across the country have often struggled to connect with rural and suburban voters.

Aides argue that O'Malley, a constant presence in the expansive Baltimore media market, enters the race far better positioned than most.

The latest independent polling on the race, conducted in April for the Baltimore Sun, showed O'Malley beating Duncan in a primary contest and with a slight lead over Ehrlich in a general election matchup. Duncan's campaign produced a recent survey showing a somewhat tighter race.

Baltimore Mayor Martin O'Malley waves to supporters during a June fundraiser. O'Malley (D) said he will announce his candidacy next week.