Philadelphia ? When Pennsylvanians go to the polls on Nov. 2, they will have to do more than choose a new governor to succeed term-limited Democrat Edward Rendell; they have to break one of two historical precedents.

If they choose Democrat Dan Onorato, the 49-year-old elected executive of Allegheny County (Pittsburgh), they will end a 64-year period in which the governorship has alternated between the parties every eight years.

On the other hand, if Republican Attorney General Tom Corbett, the early favorite, wins, he will have succeeded where every other attorney general who tried for the top job failed.

Because the history of this office is weighty in terms of national politics, with figures like Rendell, Tom Ridge, Dick Thornburgh, Milton Shapp, Bob Casey and Bill Scranton all playing prominent parts in their parties, the outcome may be more important than the highly publicized fight for Arlen Specter’s Senate seat. But because both candidates come out of the West and neither is well-known in the Philadelphia media market, where 40 percent of the voters live and elections are usually decided, both spent last weekend shaking hands and rubbing shoulders at neighborhood events in this city — classic retail campaigning in a race that only this week has moved into TV advertising.

Onorato, who was something of a surprise winner of the four-way Democratic primary and is now in his first statewide race, concentrated on African-American street festivals in South and West Philly. While Democrats have a statewide registration edge of 1.2 million voters, Onorato, a lawyer-accountant from a big Italian family who talks a managerial brand of politics, is heavily dependent on others to gin up the turnout he needs in Southeast Pennsylvania.

Rendell, whose popularity has slumped elsewhere in the state, retains his following in the Philadelphia suburbs and will boost Onorato there. Onorato was happy to see Philadelphia Mayor Michael Nutter show up at one of the street festivals. “People are angry,” Nutter told this reporter, “but they’ve got to understand it’s still an important choice.”

The long recession has blighted Democratic chances here, as elsewhere, but Pennsylvania has fared somewhat better than other industrial states — and Pittsburgh better than the rest of the state. That’s allowed Onorato to brag that he has not voted for a property tax increase in all his years on the city council and as county executive.

And that provides Corbett with his opening. A career prosecutor who served as U.S. attorney before winning twice as AG, Corbett, 61, is silver-haired, portly and looks more like a governor than the buzz-cut, balding Onorato. His claim to fame is that his investigations of corrupt legislators have so far sent several of them to jail.

In this race, he has modeled himself on Chris Christie, the freshman governor of New Jersey, promising, like Christie did, to oppose new taxes and to shrink state government. Corbett’s lineage is in the great tradition of Pennsylvania moderates. He was recruited to help run George H.W. Bush’s first campaign by Elsie Hillman, the grand dowager of the GOP who, with her wealthy husband, sponsored two generations of Republicans from Hugh Scott and John Heinz down to Specter and Ridge.

Faced with a “tea party” challenger in the primary, Corbett moved right, signed Grover Norquist’s no-tax pledge, joined a lawsuit challenging the legality of the Obama health care bill and signed an amicus brief in support of the Arizona immigration law, creating issues in the moderate suburbs. In a gaffe certain to be exploited by the Democrats, he also said to an interviewer that employers had told him workers were turning down job offers in favor of drawing unemployment compensation. “The jobs are there,” he said, “but if we keep extending unemployment, people are just going to sit there.” He later apologized for the remarks.

Corbett interrupted his handshaking Sunday at the Reading Terminal, a collection of farmers’ markets and restaurants, to visit with his only daughter, a Philadelphia prosecutor, and her husband, an African-American anti-narcotics cop. Then it was on to a German-American festival and the annual Philadelphia Republican organization summer picnic — where prospects for a good November soared so high the band even stole the Democratic anthem, “Happy Days Are Here Again.”

— David Broder is a columnist for Washington Post Writers Group. davidbroder@washpost.com