Thompson's victory in the largely Democratic city of 50,000 is all the more stunning because in political circles Reed was viewed as an Ed Rendell-like figure, helping lift Harrisburg's downtrodden - some called it downright seedy - downtown into a regional destination much as Rendell did for Center City when he was mayor in the 1990s.
Reed, mayor since 1982, could not be reached for comment yesterday.
"When I first began, we had the second-most-distressed city in the nation," Reed, 59, told supporters Tuesday night after it became apparent that he would not capture an eighth term. "Today, Harrisburg is a vastly different and better place to live and work."
But missteps have severely tarnished his image in recent years. The high cost to upgrade the city's trash incinerator continues to be a major drain on taxpayers, and the recession has only added to those fiscal woes.
Many believe Reed's obsession with museums - and one ill-fated idea in particular - did him in.
Reed spent about $8 million in public money collecting artifacts for his brainchild: a National Museum of the Old West to be built in the city. He bought about 10,000 items - including photos of Geronimo, stagecoaches, and a working Gatling gun - though Harrisburg is 1,000 miles from any point even remotely considered western.
The museum was never built, and Reed succumbed to public pressure in 2007 and started auctioning the items. To date, the city has sold a third of its collection, recouping about $1.6 million.
All along, Thompson, who has served on the City Council for nine years, the last two as president, was one of his most vocal critics.
"People have had a mayor in office for 28 years, and if you serve that long you are bound to make mistakes and lose touch with the very people you are expected to serve," she said yesterday, still bubbling over her upset victory.
Fred Clark, a Harrisburg lobbyist and longtime Reed supporter, said the mayor had run into "the perfect storm."
Thompson homed in on issues such as the Old West museum and tapped growing dissatisfaction with Reed, who is white, in the African American community, which makes up about 55 percent of the city's population.
Add the fact that many voters didn't live here when Reed's policies turned the city around, and you have an unexpectedly lopsided defeat, Clark said.
"I think we live in a society in which 'What have you done for me lately?' still exists," he added.
Rendell, who supported Reed and appeared at a fund-raiser for him last week, said yesterday that the mayor "had spent decades serving the interests of the people of Harrisburg with great energy and single-minded vision."
"But politics is not a life-affirming occupation when voters are interested in change."
Complete but unofficial results show Thompson with 55 percent of the vote to Reed's 39 percent. A third candidate, Les Ford, drew 6 percent.
There is still a chance that Reed captured the Republican nomination as a write-in candidate. He would need nearly all 435 write-ins cast to defeat Nevin Mindlin, the only Republican on the ballot.
County election officials are not expected to have a final tally for several days. Even if Reed got the GOP nod, it was unclear whether he would run, a spokesman said yesterday.
Contact staff writer Mario F. Cattabiani at 717-787-5990 or firstname.lastname@example.org.