WAS MILTON just a warm-up act?

With the primary election over, Mayor Nutter can celebrate an easy win over former state Sen. T. Milton Street, who raised no money and still owes more than a million bucks in back taxes.

But Nutter's margin of victory - he took 76 percent of the vote to Street's 24 percent - has left the general-election door cracked open for a third-party candidate. And a close look at the returns shows that Nutter's support is softest among many of the city's African-American voters.

All of this creates an opening for former Mayor John Street, a frequent critic of Nutter, who upped the ante yesterday by telling the Daily News that he will "seriously consider" a run as an independent for mayor or for City Council at large in the Nov. 8 election.

Street seemed encouraged by the number of voters who turned out for his older brother.

"That may be a distinction without much difference, but it does provide a healthy base upon which to build a campaign," Street said in an email. "Mayor Nutter has not yet created a vision for the city, nor has he even come close to announcing a plan to get there."

Although Nutter won the primary by a substantial margin, the results confirmed what polling has shown over the years: that his support is weaker among African-American voters than among white voters. In many of the city's most densely African-American wards, Milton Street pulled more than 40 percent of the votes.

Nutter's spokeswoman, Sheila Simmons, said that some of that result could be attributed to the city's economic decline.

"For the most part, the mayor received overwhelming support," Simmons said. "What he has said in the past is that he understands that there is anger out there and there is pain out there tied to the financial picture, and certainly it hits African-Americans harder."

A close look at five predominantly African-American North Philadelphia wards where Milton Street took more than 40 percent of the vote suggests that they were likely never Nutter strongholds to begin with. A review of the returns in the 2007 primary showed that in each of those wards, U.S. Rep. Chaka Fattah and state Rep. Dwight Evans took more votes combined than Nutter.

Political analyst Ken Smukler said Nutter may not have been able to win over those voters due to the city's economic woes.

"It may be, in fact, that this has always been the weakness for Nutter, not caused by anything he did in office," Smukler said. "It's possible because of the economic downturn there really was no way to overcome the weakness."

Smukler said that the results could provide an opening for a general-election candidate but that the situation would best help someone who could also attract Republicans.

"I think the problem that [John] Street has, is he probably doesn't get 100 percent of the Republican vote," Smukler said.

John Street switched his registration from Democrat to independent on April 18 on the deadline for candidates who want to make an independent run in the general election. He would need to file at least 1,845 signatures on nominating petitions by Aug. 1 to land a spot on the Nov. 8 ballot.