On a crisp October afternoon, Montgomery County Executive Douglas M. Duncan is loping through shady neighborhoods near his Rockville town house. The size 13 Nikes thud as they propel his 6-foot-4 frame along shady sidewalks and busy streets. His T-shirt is drenched from exertion. He uses it to wipe the sweat from his eyes.

The lunchtime run has become a workaday ritual for Duncan (D), and for those who know his idiosyncrasies, a possible harbinger of a coming campaign. So his three-mile loop has prompted some to wonder: Is he running because he's running? Is this the start of his candidacy for governor?

In short, yes. Advisers and political colleagues say that, for all intents and purposes, Duncan has begun campaigning for the Democratic gubernatorial nomination to be decided three years from now. No formal announcement is in the offing. But Duncan acknowledges that the race is on, and, if he is to have a chance in the emerging field of well-funded rivals, he must begin taking decisive steps in that direction.

"Right now it's governor--I am very strongly considering it," said Duncan, cooling down from his jog last week. "I'm raising money, traveling around the state to get my message out and [to] introduce myself."

Duncan's recent routine fairly shouts that he has started reaching toward Annapolis less than a year into his second term. His schedule takes him far outside Montgomery to address business groups and social-service advocates. He has mended relations with a County Council he wants on his side during the next three years and, if necessary, to bear witness to his accomplishments during a statewide race. And he has two fund-raisers--including a $1,000-a-person event--scheduled over the next month.

More telling, perhaps, is that Duncan is sketching out a set of statewide issues involving education, economic development and transportation policy that distinguish him from the presumed frontrunner, Lt. Gov. Kathleen Kennedy Townsend (D). His paid political consultant, Anita Dunn, also advises presidential candidate Bill Bradley, and she has told Duncan to watch the presidential contender's upstart campaign for ideas on how to position his own bid.

In recent weeks, Duncan has ratcheted up his criticism of Townsend and Gov. Parris N. Glendening (D) for opposing the intercounty connector road and for what he says is a lack of attention to the state's high-tech industry and to the crowding within state juvenile detention centers. Townsend manages economic development and public safety policy for the administration.

"I think he's already made up his mind, and that's what you are seeing in what he is doing," said State Senate President Thomas V. Mike Miller Jr. (D-Prince George's).

Miller and others say Duncan is being forced to declare his intentions--through deeds if not words--earlier than usual for the 2002 elections because of aggressive undeclared campaigns being waged by at least two of his presumptive rivals.

Townsend and Baltimore County Executive C.A. "Dutch" Ruppersberger III (D) have raised far more money than Duncan's $230,000, and Townsend is cultivating fund-raisers. One of Maryland's most prolific rainmakers, pharmacy mogul Michael Bronfein, is putting together a $1,000-a-person event for Townsend in the coming weeks.

"Kathleen has been working extremely hard, covering the state, and she is gaining support and credibility in all areas," said Nathan Landow, a Bethesda developer who has raised money for Townsend and Duncan in the past. "It would certainly have any potential candidate such as Duncan concerned about getting a show on the road."

Stewart Bainum Jr., a former state senator and prominent fund-raiser, said he has been contacted by Ruppersberger to schedule an introductory meeting. He also has met with Townsend, who did not specifically bring up her campaign during the talk.

"Look, I told them if Doug runs then I am obviously going to support him," Bainum said. "And I am increasingly convinced he is going to."

So are many others who watch Maryland politics. At party dinners and networking breakfasts from Frederick County to Southern Maryland, Duncan has been presenting his resume: AT&T executive, Rockville mayor and five years running Maryland's largest jurisdiction.

In his current job, he runs an operation that spends more than $1.6 billion a year, oversees a 1,000-officer police force and commands a perch from which to drive most policy initiatives. He said lieutenant governor and comptroller, a job he was offered by Glendening last year after the death of Louis L. Goldstein, do not offer the same opportunities. He either wants to be governor or run for county executive again.

"I see a lack of leadership coming out of Annapolis, a walking away from our transportation problems, a lack of understanding of the new economy," Duncan said. "I see this economic divide between our part of the state and the Baltimore area, the Eastern Shore and Western Maryland. . . . We can make great improvements over where we are today."

Twice this month, Duncan is addressing Baltimore business groups with his talk on economic development, which sounds suspiciously like a stump speech. At a breakfast last week with the Greater Baltimore Economic Forum, he described the Glendening administration's opposition to the intercounty connector, a $1 billion road that would connect Interstate 270 with Interstate 95 north of the Capital Beltway, as "the worst kind of special-interest politics." The talk was titled: "Duncan Means Business."

"I am more and more discouraged every day with the lack of leadership we are seeing from Glendening/Townsend," he told the group. "We need a much more focused statewide economic development effort. We're not there yet, and over the next three years I don't see much happening to change that."

After that speech, Duncan traveled to Howard County to lobby the Maryland Interfaith Legislative Committee to support two proposals he plans to push in the next General Assembly session: expanding the state income tax credit for poor residents and creating subsidized health insurance for adults whose children are covered under federal plans.

Those who know him say one indicator of his seriousness is that he is back on his exercise regime. Since June 23, Duncan has missed only 10 days of exercise. He started by walking a course that takes him behind the Rockville Senior Center to a finish at Woodley Gardens Park. He's now picked up the pace to a slow run after shedding some weight--more than 30 pounds.

Good-natured about his weight--he commonly uses his appetite and girth as a joke in public appearances--Duncan nonetheless understands the aesthetic demands of a modern campaign. He also feels better weighing less; he suffers from a herniated disk in his back.

"I like it a lot more than I did when I started," Duncan said. "I'm 43. My wife has been telling me to exercise for my health. But I have a long way to go. I jog. I still don't call it running."

Politics follows him along the route. This summer he was stopped by a man in a pickup truck waiting for him along Route 355. He asked Duncan to ride with him to his office to see a four-foot-tall scale model of the intercounty connector he had built and discuss the subject. Duncan demurred.

But the connector has inspired Duncan and given him an easy-to-understand issue that his own polls suggest has broad support.

"You get a sense that it is kind of the first move in the governor's chess match," said Keith Haller, whose company Potomac Survey Research has polled extensively on the subject. "Duncan feels like he has Townsend boxed in on the ICC. We'll see how adept she is in her next maneuvers."

As those and other maneuverings takes shape, Duncan is hoping for a big field to emerge for the 2002 nomination. It could improve his own chances, coming as he does from such a large county, but he says there are others reasons.

"If [U.S. Rep. Benjamin] Cardin, [House Speaker Casper R.] Taylor, [Prince George's County Executive Wayne K.] Curry, Dutch and Townsend all run--what a race," Duncan said, puffing along his route. "That would be a lot of fun."

CAPTION: Douglas M. Duncan now exercises daily, a move some say is in preparation to run for governor.