A big campaign endorsement for an independent candidate for City Council on Tuesday could develop into a major political headache for Mayor Nutter.

Nutter endorsed Andrew Stober, a former member of the his administration, who is vying in the Nov. 3 general election for one of the two at-large City Council seats reserved by law for members of minority parties. Traditionally that has meant Republicans.

But Nutter is not just the mayor. He is also the West Philadelphia 52d Ward's Democratic leader, a post he has held for a quarter-century.

The Democratic City Committee's bylaws say party officials can be disqualified from holding their posts if they have "within a two-year period actively or inactively supported the candidacy at any general election of any person or persons not on the Democratic ticket."

A spokesman for U.S. Rep. Robert Brady, the city's Democratic Party chairman, confirmed that Nutter's endorsement violates those bylaws.

City Council President Darrell L. Clarke, also a Democrat and a former ward leader, said he found Nutter's actions "perplexing."

Nutter on Tuesday also endorsed three Democratic nominees for City Council at-large, incumbents Blondell Reynolds Brown and William K. Greenlee and newcomer Derek Green. He did not endorse two other Democratic nominees, newcomers Helen Gym and Allan Domb.

Voters can select five candidates for the seven at-large Council seats.

The five Democratic nominees are virtually assured a general election victory since their party holds a 7-1 voter registration advantage over Republicans and independents in the city.

"As the mayor, it's his right to endorse whomever he pleases," Clarke said. "But as a member of the Democratic Party, as a long-serving ward leader, it's somewhat perplexing."

Clarke noted that Nutter's action came one day after the Democratic City Committee's annual preelection cocktail party.

"The mayor actually spoke about getting out the vote for the ticket," Clarke said of Monday's event. "You'd like to see some consistency."

Nutter, through a spokesman, said he "appreciates all the concern and perspectives that have been expressed" about his endorsement of Stober. He added that the endorsement was meant for one of the two at-large seats usually won by Republicans.

"City voters have an opportunity to elect a very talented, independent candidate for one of those seats," Nutter said.

Brady's spokesman said the next step to address a bylaw violation could be to have the party's Policy Committee hold a hearing to act as a fact-finder to examine Nutter's actions and then make a determination for any potential consequences.

There is precedence for stripping a ward leader of his party position.

The Democratic City Committee did that in 1999 after John Sabatina Sr., leader of Northeast Philadelphia's 56th Ward since 1980, backed Republican Sam Katz for mayor over former Council President John F. Street.

Sabatina responded by having his wife seek the post of ward leader in 2000. She won and he eventually took back control of the ward, a post he continues to hold.

Nutter, speaking outside his City Hall office Tuesday morning, said it was the first time he had endorsed an independent candidate. Former Gov. Ed Rendell joined Nutter in endorsing Stober.

"This is one of these situations where a person's track record is clearly much more important than what their voter registration card says," Nutter said. "Andrew Stober represents all of the best in Democratic principles."

The endorsements are a major pickup for Stober, a lifelong Democrat who changed his registration and resigned his post as chief of staff in Nutter's transportation office to run.

Nine people are vying for the two at-large seats, typically won by Republicans. The Republican candidates are incumbents David Oh and Dennis O'Brien and challengers Terry Tracy, Daniel Tinney, and Al Taubenberger.

The third-party candidates are Stober; Kristin Combs, a member of the Green Party; Sheila Armstrong, an independent; and John Staggs, a member of the Socialist Workers Party.

While Stober's campaign has drawn attention, he still has relatively low name recognition and is running in what will undoubtedly be a weak-turnout race. Stober said his campaign has also battled to educate Democrats unaware that they can vote for an independent.

"Having the endorsement of two of the most respected Democrats in the city, Mayor Nutter and Governor Rendell, there's probably nothing better to explain to Democrats why they should be supporting me than those two endorsements," he said.

Rendell said he thought Stober would bring a "fresh perspective" to Council.

"He's young and he's energetic and he's not tied to the politics of the past," Rendell said. "So I really would like to see him win."