Republican city council member Frank Rizzo Jr. knows about racially divisive political campaigns. His father and namesake became mayor here in the early 1970s by running as the tough white cop who'd restore law and order. He won elections that divided the city in half.

Rizzo is loyal to his father's memory, but on election night here Tuesday, he did a gracious thing: He allowed that he preferred the gentlemanly encounter between victorious Democrat John Street, who is black, and Republican Sam Katz, who is white, to battles his father fought.

"I'm so impressed with the quality of this campaign," Rizzo said in an interview at Katz's election-night party, even as the returns showed his man losing. "My dad's campaigns were a rougher type of campaign. We had double-digit inflation and civil unrest. It was a different time, and I thank God that we live in a different time now."

This week's mayoral race may be a perfect indicator of the paradoxes of big-city racial politics at the end of the century. On the one hand, Rizzo's description of the election is absolutely fair: In a contest that had all the ingredients of a racial donnybrook, Street and Katz declined to play the game.

They ran substance-heavy campaigns in which each, in his different way, promised to join the ranks of the moderate, problem-solving mayors who have become the norm over the past decade. One of those mayors is Philadelphia's Ed Rendell, who is retiring this year. In a late-night interview on the eve of the vote, Rendell paid tribute to both men.

"Neither one has done anything to appeal across racial lines," Rendell said. Yet when the votes came in, race was indelibly etched onto the columns of numbers that added up to Street's narrow victory. Street carried the city's black wards with margins in the range of 95 percent, and on a strong turnout for a rainy, blustery day. Katz, a moderate who treated his Republican label as an inconvenience to be ignored, won the white ethnic wards by 8 to 1.

The difference--Street doing slightly better among whites than Katz did among blacks--was, along with the outpouring of black support, the key to the result. It owes a good deal to the surprising endurance of Democratic Party identification. Party loyalty is not what it used to be, but it is not irrelevant.

"Vote Straight Democratic" might thus have been Street's most effective slogan. Party loyalty was reinforced by Rendell's frenetic last-minute campaigning and President Clinton's visit to rally the troops in the final days. And the hard work of the unions and the remnants of the city's Democratic machine managed to cut Katz's margins in the white wards just enough.

"If we lose, the only thing it proves is that it can't be done," James Baumbach, Katz's campaign manager, said as the first returns trickled in. The impossible "it" in question is electing a Republican mayor here.

That sounds self-serving, but it's not. As Rendell noted, Katz ran a "terrific" campaign. He created excitement with his promises to cut taxes, fix the schools and attract businesses and middle-class taxpayers to a city that is losing both.

Katz's role models included the bookish and innovative Steve Goldsmith, Indianapolis's outgoing Republican mayor. Goldsmith happens to be George W. Bush's domestic policy adviser, who aims to give the Texas governor's campaign speeches a visionary cast. Bush might note that although Indianapolis's city hall fell to the Democrats on Tuesday, Katz's appropriation of Goldsmith's ideas nearly sold in this Democratic city.

The paradox is that Street may be better able than Katz to carry out Katz's promise of reform, because Street is in a strong position to unify the city. It's clear that many African Americans felt Street's long service in politics and his loyalty to Rendell earned him a chance at the top job. Street himself acknowledges his personality is prickly, but not even his opponents doubt his competence or his basic conservatism on fiscal issues.

His supporters reasoned that if Street didn't deserve a shot, who did? It's no wonder that at Street's victory celebration in the early hours Wednesday, Rendell pointedly reminded the victor's supporters that much of the city's "establishment" had stood with the mayor-elect.

Racial solidarity at voting time need not lead to racial division. White ethnic groups, after all, are no strangers to the electoral tug of group loyalty. But because Street and Katz campaigned as they did, the new mayor has an opportunity to be the conciliator who extends the lease practical innovators now hold on city politics all over the country.