The to-do list for the next mayor of Philadelphia is a daunting one: slow a surging homicide rate and change the pay-to-play culture in City Hall.

With less than a month to go before the Democratic primary, a retired businessman with deep pockets, two congressmen, a former city councilman and a veteran state representative all say they can handle the challenges and turn the city's fortunes around.

But with nearly a quarter of voters still undecided, the mayor's office remains up for grabs. The incumbent cannot run, no one has an insurmountable lead in the polls, and everyone is within striking distance.

With five viable candidates in the election — all under pressure to reduce crime and corruption — the election looks promising for those in the city hoping for change, said Randall Miller, a political analyst at St. Joseph's University.

"Clearly, they are suggesting that, 'We were not part of this problem,"' Miller said.

The Democratic nominee who emerges from the May 15 primary will face Republican Al Taubenberger, a Chamber of Commerce president, and is all but guaranteed to win the general election in November. Nearly four out of five Philadelphia voters are Democrats and the city hasn't had a Republican mayor in 55 years.

Millionaire former health care executive Tom Knox holds a slight lead in the polls, running as an outsider who promises to take a "For Sale" sign off City Hall.

U.S. Reps. Bob Brady and Chaka Fattah are touting their leadership and congressional records, while state Rep. Dwight Evans is pointing to his legislative accomplishments in Harrisburg. Former Councilman Michael Nutter has sought to build on his reputation for challenging the policies of Mayor John Street, who cannot seek re-election because of a two-term limit.

Knox's anti-establishment TV blitz has set the tone, leading others to follow suit. Each sells himself as a fresh face — even Brady, the longtime head of the city's Democratic machine, and Fattah, whom many view as closely allied with the incumbent.

All have campaigned on hiring more police or on other measures aimed at slowing a homicide count that topped 400 in 2006 and has shown no signs of slowing. More than 100 homicides have already been recorded this year.

Either directly or indirectly, each candidate has spoken about the need for a new start in a city rocked by a long-running corruption scandal. Nearly two dozen people have been convicted since an FBI bug was found in Street's office before the 2003 election.

Both the murder rate and corruption convictions have hurt Street's legacy, even though he was never charged in the FBI probe and has argued he has done everything he can to fight crime.

"We have had the person who has probably been the best-prepared person to become mayor," District Attorney Lynne Abraham said of Street, a former city councilman. "As well-prepared as he's been, he has not done the kind of job that people wanted of him or expected of him."

Abraham is campaigning for Brady and says the city needs a proven unifier like the longtime Democratic party chairman.

But Brady has had the toughest road so far. He's been stuck fighting a Knox-led effort to knock him off the ballot over flawed nominating paperwork.

"The court challenge has hijacked the mayor's race," said Sam Katz, who lost to Street as a Republican in a landslide in 2003, when the discovery of the bug led voters to flock to Street's defense. Katz has since left the party just in time to qualify to run for mayor as an independent, but won't say whether he will run.

Knox, a former deputy mayor under current Gov. Ed Rendell, is maintaining a lead in polls on the back of a self-funded spree of television ads. Fattah, the favorite heading into the race, has dropped back but recently stepped up TV advertising.

The racial makeup of the field muddles the electoral picture in a city where votes nearly always fall along racial lines. Evans, Nutter and Fattah are black, while Knox and Brady are white.