White was expected to endorse Katz today during an 11 a.m. news conference at Katz's headquarters in Center City. Both Katz and the Democratic mayoral nominee, John F. Street, met with White late last month in hopes of picking up his endorsement.

Yesterday morning, a group of White supporters met in the offices of Blank, Rome, Comisky & McCauley, a Center City law firm, to discuss whom he should endorse. The meeting was at least the fourth in a series of such sessions this summer among White supporters.

White, a former state secretary of welfare, addressed the group, according to one participant, and said that he was torn and that the decision was very difficult for him.

Conventional wisdom would suggest that White should endorse Street.

The two Democrats are friends, and both are African American. They worked together from 1993 to 1997 when White served as executive director of the Philadelphia Housing Authority and Street, as City Council president, was vice chairman of the agency's board.

Further, while Street ran a largely positive primary campaign, Katz - who was unopposed in the Republican primary - inserted himself into the Democratic primary in an obvious attempt to choose his opponent in the general election. Katz aired a series of TV commercials that attacked White and the other leading Democrat in the primary, Marty Weinberg. One of the spots attacked White's stewardship of PHA and management of the state Department of Public Welfare.

White, who won 22 percent of the vote in the May primary, fared well among progressive whites and middle-class black voters whose support could make a difference in the November election.

Realizing the importance of the White endorsement, Katz labored over the summer to woo White, and the effort seems to have paid off.

"There was a lot of personal work done by Sam," said a member of the Katz campaign who spoke on the condition of anonymity.

He added that the Katz forces were hopeful White's endorsement would encourage other Democratic voters to back the Republican nominee.

"It's important. It's unprecedented," the Katz campaign aide said. "John [White] is influential in his own right, and he sends a very powerful signal to people that you really have to put the city first. It's not about politics. It's not about race. It's about performance."

But race will play an important role in the general election.

Katz, who is trying to become the first Republican in five decades to be elected mayor, is white. He is expected to receive a majority of the white vote. Similarly, Street is expected to receive a majority of the black vote.

The thinking among political analysts is that White's endorsement could help Katz pick up support among liberal blacks and progressive whites from areas such as Mount Airy, Germantown and West Oak Lane. White was endorsed by the teachers' union and the city's white- and blue-collar unions during the primary.

Such voters were the heart of White's electoral base, and they are considered an important element in the general election.

"Sam Katz is a Republican who has to get Democratic votes to win. And he just got one," said Larry Ceisler, a political consultant. "If the White endorsement is followed by others, basically opening up the floodgates, then it becomes very important."

Since May, Street has sought to unify the Democratic Party, with mixed results. He invited his four defeated rivals to join him for lunch at The Palm the day after the primary election, but only Dwight Evans showed up.

Only Weinberg has appeared at a news conference with Street to give an endorsement.