ROCKVILLE — ROCKVILLE -- State Sen. Mary H. Boergers became the first candidate to officially launch a campaign for governor yesterday, portraying herself as the champion of voters fed up with power politics in Annapolis. "I'm not running as an outsider, I am an outsider," the Montgomery County Democrat told about 100 cheering supporters outside Rockville High School, where she taught U.S. government before entering politics. "I've been in Annapolis 12 years. I know how the system works, but I've never been a part of it and I never will be," she said. "I've stood up for what I believe in regardless of the political consequences." Ms. Boergers, 47, is the least known of the three announced candidates for next year's Democratic gubernatorial nomination. She faces an uphill battle against Lt. Gov. Melvin A. Steinberg and Prince George's County Executive Parris N. Glendening, both of whom have raised more campaign money and have wider followings. Ms. Boergers, with appearances throughout the state yesterday and today to formally begin her campaign, begins a major effort to raise her profile outside Montgomery County in anticipation of the September 1994 primary election. In Rockville, and later at Canton Waterfront Park in Baltimore, Ms. Boergers denounced the state's political establishment -- the "power brokers," as she described them -- and hurled phrases such as "abuse of power." Under questioning, however, she declined to identify by name the individuals and institutions to which she was referring. "I don't think it's appropriate," she said. In addition to its anti-establishment flavor, Ms. Boergers said, her campaign will stress at least three themes, education, crime and the economy, with emphasis on the port of Baltimore, which she described as the "economic engine" for the state.