The last time a Republican named Bush ran for president against a Massachusetts Democrat, a filthy Boston Harbor (search) was transformed into one huge campaign prop.

Vice President George H.W. Bush's (search) 1988 tour of what he dubbed the "Harbor of Shame" was a piece of political theater aimed at embarrassing his opponent, Democratic Gov. Michael Dukakis (search), in his own backyard.

Today, as Bush's son takes on Sen. John Kerry, Dukakis' former lieutenant governor, a rejuvenated Boston Harbor looks nothing like a campaign issue.

A harbor once buried in sludge from centuries of sewage dumping now teems with plants and animals, including real fish and seals. Human waste and toiletries no longer float past boaters. Swimmers can take to beaches without fear of a follow-up trip to the hospital.

The harbor has been transformed from the city's outhouse to a showpiece more quickly than anyone expected.

"It's really profound what happened," said Rick McKenna, a boat owner who worked on the harbor in the mid-1980s. "A lot of people just gave up on the harbor."

The harbor dumping began with the settlement of Boston in 1630, and was actually an improvement over past practices such as leaving waste in streets.

A strong tide that flushes out the harbor twice daily kept the dumping from becoming a major issue for centuries. But growing populations in the 43 communities that once poured sewage directly into the harbor eventually overwhelmed the natural process and transformed the harbor into a cesspool.

When the dumping stopped in 1991, the harbor was essentially allowed to cleanse itself.

"It really is that simple," said Andrea Rex, director of environmental quality at the Massachusetts Water Resources Authority (search), which directed the harbor cleanup.

The court-ordered cleanup came at a price of $3.8 billion, so far. Water and sewer customers have shouldered about three-quarters of the bill, and not always quietly. In the early 1990s, homeowners burned their bills and dumped them in the harbor in protest.

The cleanup's centerpiece is the Deer Island waste treatment plant (search). The facility separates the solid and liquid waste, then pumps the treated water through a 9.5-mile pipeline that empties into Cape Cod Bay (search). The plant, which became fully operational in 1995, treats an average of 350 million gallons of sewage a day.

The resulting sludge, produced at a rate of 90 tons daily, is converted to high-grade fertilizer. The remaining water is disinfected and sent through the pipeline.

Eugene Gallagher, an ocean-sciences professor at the University of Massachusetts at Boston, said a lifeless "black mayonnaise" sludge that covered the harbor bottom was replaced in months by a "shag rug" of tiny pollution-tolerant organisms called amphipods, which broke down the toxic top layer of the sludge and "irrigated" it with oxygen. That encouraged the growth of sludge-eating bacteria.

"It's just been an absolutely amazing recovery," he said.

The inner harbor is still plagued by industrial pollution, while outdated sewer systems along the harbor contribute to frequent summer beach closings.

Boat owner McKenna, 39, knows problems remain, but he could barely contain his enthusiasm about the improvement during a recent tour of the harbor on his boat.

On this day, cormorants flew nearby, fish swam below the slate-blue surface. These days, he would welcome a repeat visit to the harbor by a Bush.

"I'd like to take him out on the boat," he said. "I'll take him fishing."