Jack B. Johnson was sworn in as Prince George's county executive yesterday, promising to unite the county around a broad agenda of improving public education and reducing crime.

On a day of wide-ranging political change in the nation's largest black middle-class suburban enclave, Johnson said he would seek to raise teachers' pay, clean up trash-strewn neighborhoods and provide health care for 90,000 uninsured county residents.

But Johnson laid out few details on how he would meet those goals. And he made no mention of the issue that formed the centerpiece of his campaign: reforming a police force under federal investigation for allegations of brutality. When he spoke of the police, Johnson said that the county's future "is linked directly to our ability to combat crime."

"I am committed to providing the necessary resources for our law enforcement efforts and to stop crime before it occurs," he said during his 25-minute address before a large crowd at the Show Place Arena in Upper Marlboro. "As we eradicate crime, we will create more opportunity for development and attract high-quality businesses we all desire."

Johnson's swearing-in marked the end of Wayne K. Curry's eight-year reign as county executive, and it came on a day when the county underwent its most significant political change since the term limits law was enacted a decade ago.

Several Maryland counties swore in new executives or welcomed incumbents back for new terms yesterday. In Baltimore County, James T. Smith Jr. (D) succeeded C.A. Dutch Ruppersburger (D), who was elected to Congress. Douglas M. Duncan (D) took the oath for an unprecedented third term in Montgomery County, and James Harkins (R) began another term in Harford County. On Sunday, Anne Arundel County Executive Janet S. Owens (D) was sworn in for her second term.

In Prince George's, five new members of the all-Democratic County Council were sworn in during the morning ceremony: Camille Exum (D-Seat Pleasant), Samuel H. Dean (D-Mitchellville), David Harrington (D-Bladensburg), Douglas J.J. Peters (D-Bowie) and Marilynn Bland (D-Clinton).

The new lawmakers join Tony Knotts (D-Temple Hills) and Thomas E. Dernoga (D-Laurel), who won office during special elections this year, as well as Peter A. Shapiro (D-Brentwood) and Thomas R. Hendershot (D-New Carrollton), who are beginning their second terms.

In the afternoon, Glen Ivey was sworn in as state's attorney, replacing Johnson.

For Johnson, 52, a former tax lawyer who grew up on an island off Charleston, S.C., the ascendance to the county's top elective office is a high point in a political career that began eight years ago when he captured the state's attorney's post.

Over the years, he cultivated a reputation as a tireless campaigner, spending nights and weekends dropping in at awards dinners, barbecues and church services.

At the same time, he developed a wide network of community and church leaders in the county's poor and working class communities -- ties that formed the heart of his campaign for county executive.

After defeating four opponents in the Democratic primary, Johnson last month easily beat Republican Audrey E. Scott in the general election.

During the campaign, Johnson stressed the importance of improving schools and reducing crime.

He spoke of the need for police reform, an issue that brought him into continuous conflict with the county's police union. After his victory, Johnson tapped Patrick Murphy, a former New York City police commissioner, to propose reforms for the police department.

But when he introduced Murphy to the crowd at yesterday's swearing-in, Johnson appeared to tone down his message, saying only that the former commissioner would help "us in achieving our law enforcement goals."

After the speech, Johnson said there was no significance to his omission of police reform.

"Everyone knows what my position is on that," Johnson said, adding, "It's time to talk about the other issues."

The public, he said, "will begin to see a different side of me, one that's a unifier and a leader."

Indeed, during the speech, Johnson dwelt on the importance of uniting a county that in recent years has been beset by political infighting.

The nadir came this year, when the Board of Education warred with Superintendent Iris T. Metts -- a battle that culminated in the state legislature replacing the elected board with a panel of appointees.

"Benjamin Franklin knew well how a divided people could destroy the very heart and soul of a community," Johnson said. "Later, Mahatma Gandhi, Nelson Mandela and Dr. King would struggle with the very same precepts, that unless there is unity in purpose, a community could not long endure. They remind us that a divided house cannot stand."

Political and community leaders said that Johnson set a constructive tone.

"This is not a sprint; it's a distance run. The details will come," said Del. Anthony G. Brown (D-Prince George's). "He has good personal relationships with a lot of elected officials, and that's 90 percent of this business."

Eugene W. Grant, a Seat Pleasant community activist and a member of the police chief's advisory board, said Johnson's connection to the county's poorer communities may reduce political squabbling.

"There's a sense that they have a seat at the table, that they have a voice," Grant said. "And with that, there's a base for creating unity."

Before the ceremony, Johnson waited in a room backstage, surrounded by family members and allies. After years of almost ceaseless campaigning, his moment had arrived.

Watching the scene, Peggy McGee, his longtime aide, beamed.

"Can you believe it?" she said. "We're finally here."

Montgomery County Executive Douglas M. Duncan jokes with supporter Libby Tolbert of Barnesville after he was sworn in for an unprecedented third term.Jack B. Johnson and his wife, Leslie, during yesterday's swearing-in ceremony at the Show Place Arena in Upper Marlboro.From left, new and returning Democratic Montgomery County Council members Nancy Floreen (At Large), Mike Knapp (District 2), George Leventhal (At Large), Tom Perez (District 5), Marilyn Praisner (District 4) and Michael L. Subin (At Large) are sworn in at a ceremony in Rockville. See story, Page B4.Jack B. Johnson hugs a well-wisher before being sworn in as county executive. He said he will focus on improving education and reducing crime.