With eight days to go, the Philadelphia mayoral race is becoming less a matter of who's best, and more a matter of who votes.

Both Republican Sam Katz and Democrat John Street are spending hundreds of thousands of dollars each on assembling armies of party faithful, volunteers and hired guns who will work neighborhoods and polling places a week from tomorrow.

Typically, according to political experts, these costly efforts - pros call it the field operation - only squeeze out an extra percentage point or two and only really matter in a close election.

They will matter in this one.

Numerous polls have shown that Street, the former City Council chief, and financial consultant Katz have been locked in a dead heat since Labor Day. While the two sides are launching an unprecedented $2 million ad blitz this week to sway some 15 percent of the electorate still undecided, experts doubt either will pull far ahead now.

"In a close election, there's no better bargain for your money than an effective field operation," said Larry Ceisler, Democratic political consultant and Fox-TV analyst. Ceisler saw it in 1987, the last close general election for mayor, when huge Election Day turnouts in South Philly and the Northeast fell just short of carrying the GOP's Frank Rizzo to an upset over then-Mayor W. Wilson Goode.

The conventional wisdom is that if the election comes down to getting out voters on Election Day, then Street would have a strong advantage.

Why? In recent weeks, Street has worked closely with U.S. Rep. Bob Brady, the party chairman, and other leaders to make sure that the Democratic Party, with 69 ward leaders and more than 3,000 committee members in almost every corner of Philadelphia in an effort to unite one of America's last urban political machines.

In addition, Street, Brady and others have assembled a small army of labor-union activists, led by John Dougherty of the electricians' union, that has declared a labor holiday on Nov. 2 in order to get thousands of voters to the polls.

Then, as always in Philadelphia politics, there's money. In the May primary, Street spent more than $250,000 on a get-out-the-vote operation that went in good measure through two organizations: One called Progress 2000 that was run by allies of U.S. Rep. Chaka Fattah and the North Philadelphia-based campaign of City Councilman Darrell Clarke, who was once Street's top aide.

But nothing in politics is that easy, and experts say that Street faces several obstacles on Election Day.

The biggest, according to some Democratic insiders who spoke on background, is that polls are showing some 60 percent of white Democrats are planning to vote for the GOP's Katz. That number rises to more than two-thirds in some rowhouse neighborhoods like the lower Northeast.

So what should Democratic activists in a neighborhood like Mayfair, for example, do? Tell voters to stay home? That would actually help Street, experts note, but ward leaders also must support other Democrats like City Council members Rick Mariano and Joan Krajewski, or Superior Court judge candidate Berle Schiller, whose election is a top priority of powerful state Sen. Vince Fumo.

Some voice similar concerns about the get-out-the-vote effort by the building trade unions, which are strongest in white ethnic enclaves where Katz is well ahead of Street. Campaign aides to Street say the union effort will focus on labor households which have been targeted with rallies, mailings and phone calls to keep in the Democratic fold.

Katz, meanwhile, is hoping to do something that other Republicans in Philadelphia - with the exception of former Democrat Rizzo - have not done, and that is place a strong operation of his own in the field on Election Day.

The GOP candidate starts with a serious disadvantage. The Republican structure of ward leaders and committee people - while more active than in most other major American cities - has been declining for decades since the GOP was booted from power back in 1951.

Even top party leaders concede that more than one-third of Philadelphia's nearly 1,700 election districts now lack an active Republican organization. Many of those are predominantly black neighborhoods where support for the GOP is practically nil.

However, the political consultant that many of his peers praise as possibly the best in Philadelphia at assembling a field operation - longtime Democrat Howard Cain, who has worked for Fumo and key Katz supporter John White - has signed up with the Republican nominee.

So has attorney and longtime political activist Obra Kernodle, another close ally of White who is aiding Katz on assembling an Election Day operation in places like Overbrook or Mount Airy, where the former housing commissioner - popular with upscale white and black liberal Democrats - was strong but the Republican Party is weak.

"I think it's very important," Cain said of the need for Katz to assemble a strong field operation. "They have volunteers in place who are willing to work for Sam Katz in areas of the city where the Republican Party is not as strong as we would like it."

Cain said that the Katz campaign has identified at least 850 volunteers - supporters who have contacted the office by phone, in person or even over the candidate's Web site - willing to work on Election Day, largely plugging holes where the GOP is not active.

Since Katz has run citywide before, in the Republican mayoral primary in 1991, Cain and other strategists will try to determine where Katz might have the strongest support, and target efforts there.

Of course, Street supporters have been poring over the district-by-district results from the May primary in which the former Council chief bested four rivals. The campaigns also have relied on other techniques to identify their likely voters, including phone canvassing, registration lists, and people who've contacted the office.

Political experts say that field operations are widely misunderstood. Remember, the people most interested in the political process don't need any persuasion to vote in what is shaping up as the closest mayoral race in 12 years.

Instead, the trick for both Street and Katz is to find registered voters on the fringe of the political process, living in pockets of the city where their candidate is strongest, who need a late afternoon telephone reminder, a van ride, or some other prod to get out and vote.

Most insiders are impressed with the field operation that Street has assembled. It includes longtime lower Northeast activist Mark Lopez, who was field director for Democrat Marty Weinberg, who ran second in the May primary. Lopez registered thousands of new Democrats last spring and has strong ties in areas where Street ran poorly.

It also includes Greg Naylor, who has been a top congressional aide to Fattah and who in the primary was co-leader of an organization tied closely to Fattah called Progress 2000, which spent roughly $230,000 on Election Day to bring out voters for Street and also for judicial and City Council candidates, including first-time winners Blondell Reynolds-Brown and Wilson Goode Jr.

Although Naylor is now working directly for the Street campaign, his Progress 2000 - which is strong in areas of Fattah's West Philly political base where Street had not been a candidate before this year - is going to be active again next week. Earlier this month, the Street campaign wrote the group a check for nearly $50,000.

Progress 2000, which receives little scrutiny, worked closely with a network that included both longtime Street and Fattah allies and several activists plugged into networks of young people and others who can flood the streets on Election Day.

One such person is William Mackey, who runs a well-known Philadelphia youth program called the City Wide Improvement and Planning Agency and who received $15,500 from Progress 2000 to field a group that distributed literature and performed other Election Day tasks for Street and other candidates. He said he keeps his political efforts separate from his nonprofit group.

Mackey said that during some troubled periods in his life, when he was homeless and recovering from drug addiction, "John Street helped me put my life back together."

He also praised the work of Progress 2000, saying it only backs candidates whose philosophy it supports and that "the best thing is that they give young people an opportunity to get involved in the process."