CHAKA FATTAH has grown accustomed to the sound of footsteps.

Federal prosecutors have been following the longtime Philadelphia congressman for eight years - subpoenaing his emails and congressional records, auditing his nonprofits and flipping his political confidants - as they seek to build a corruption indictment against him.

Fattah, 58, has been tapping his campaign war chest to cover hundreds of thousands of dollars in legal fees. He's in a "safe" district, so he doesn't need the campaign money to, ya know, campaign.

But now, the footsteps could be getting louder.

The folks behind Crowdpac, a nonpartisan Kickstarter-type website launched in August, are looking to instigate a political fight in Fattah's district in next year's primary. So far, they've thrown 18 people into the ring, hoping that one or more might emerge as a formidable challenger to Fattah, an 11-term Democrat who ascended to Congress in 1994 and hasn't had a close race since.

"Nobody's safe," said Crowdpac political director Liz Jaff.

That, at least, is Crowdpac's goal - to gin up competition in noncompetitive districts around the country and dilute the power of special interests by crowdfunding hesitant challengers.

Crowdpac, headed by Steve Hilton, a former senior adviser to British Prime Minister David Cameron, decided to experiment in Fattah's 2nd Congressional District after the website's staffers started to hear buzz about his legal troubles while they were working on this year's City Council races and mayor's race.

"Well, why are people not talking about running against him?" Jaff recalled thinking.

'Stir s--- up'

Crowdpac recently created a website with 18 potential Fattah challengers, including former PGW executive Doug Oliver, District Attorney Seth Williams and former Philadelphia Redevelopment Authority director Terry Gillen.

Here's how it works:

Visitors to the site can pledge money to potential candidates, and it's only disbursed if a candidate officially announces that he or she is running. By the end of June, Crowdpac plans to send each of the possible Fattah challengers a username and password, to log in and see how much money has been pledged.

Candidates are placed on an ideological spectrum based on an algorithm including from whom they've received money and to whom they've contributed, as well as their public statements and votes if they hold public office.

"These things can work. They are ways that a potential candidate can gauge how much support is out there," said Adam Bonin, a Philadelphia lawyer who specializes in election law and campaign finance. "I think anything that encourages small-dollar donors to amass themselves and have a public demonstration of where they stand is a good thing."

Crowdpac created the candidate field for the Fattah race, but soon anyone will be able to create a page and add candidates, similar to the way Wikipedia works.

"Anyone can stir s--- up," Jaff said.

Potential candidates cannot remove their names from the pages. That's by design: It provides them cover from party bosses and other political figures who otherwise might snuff out any competition to incumbents like Fattah.

Political machines typically don't like competition. This is a way around the machine.

"People have alliances," Jaff said. "If you raise the idea of running, you can easily be shot down by the political infrastructure quickly. This tool puts it out there for people. It raises the question: 'Should you run?' "

(Crowdpac says it will remove names in limited circumstances, such as if listing someone as a potential candidate causes an ethics problem in the person's workplace.)

David Thornburgh, president of the Philly good-government group Committee of Seventy, said he's been intrigued by Crowdpac's efforts.

"Competition is good," Thornburgh said. "Even if you're doing a great job, the way you keep doing a great job is if somebody keeps your feet to the fire.

"People talk about the wisdom of crowds. This is a test to see how wise they are, I guess."

Potential challengers

So, who's interested in challenging Fattah?

* Oliver, who showed an ability to connect with voters during the mayoral primary, said that "several people" have suggested he consider running in next year's congressional primary.

"While encouraging, I've not yet had a chance to think it through thoroughly, including the countless conversations that would be necessary before making a decision about that type of endeavor," Oliver said.

* Williams, the district attorney, said he loves his job, but he sounded as if he could be interested in running for Congress, Senate or attorney general at some point. Then again, Williams said he's also "very interested in opening a jazz and cigar bar in Key West."

* Gillen, who dropped out of the mayor's race in January, declined to comment yesterday.

Also listed as potential congressional candidates on the Crowdpac site:

* Mayor Nutter. He said through his spokesman that he's backing Fattah: "I will be supporting Congressman Chaka Fattah in his re-election effort as he has served his district and our city tremendously well."

* Cynthia Figueroa, president and CEO of Congreso de Latinos Unidos. She said that she is "very committed to public service" but added: "I'm really happy where I am."

* City Managing Director Rich Negrin. He said he's focused on his current job, but "in the future when I'm no longer doing this job, I'm going to look for opportunities to serve. That can take a lot of different forms." Negrin, however, added that he's interested in Crowdpac's potential to increase political competition and voter participation.

"It gets the traditional political establishment kind of out of the way a little bit in the beginning," Negrin said.

Of course, the political landscape could change if Fattah is indicted between now and next spring.

Last year, Fattah's former chief of staff Greg Naylor and political consultant Tom Lindenfeld pleaded guilty to charges stemming from an alleged scheme to conceal a $1 million loan in the 2007 mayoral race, in which Fattah was running. Prosecutors allege in court documents that Fattah, identified only as "Elected Official A," orchestrated the scheme. Naylor and Lindenfeld are cooperating in the Fattah investigation.

A Daily News review of tax records last year found that between 2001 and 2012, nonprofits founded or supported by Fattah paid out at least $5.8 million to his associates, including political operatives, ex-staffers and their relatives. Federal investigators also have looked into those nonprofits.

Fattah, who lives in East Falls, has repeatedly said he never participated in illegal activity. He declined to comment for this article, but he clearly plans to seek re-election next year.

In remarks delivered via YouTube yesterday to the Big Brothers Big Sisters National Conference, Fattah mentioned his efforts to secure federal funding for youth mentoring and said he hoped to do "even more over the next decade."

'You run faster'

If the Crowdpac model catches on, Jaff said, it could change the way money is raised in politics nationwide and could weaken the power of traditional political machines - such as Philadelphia's Democratic City Committee - that usually protect incumbents.

"We have these people that just sit there," Jaff said of longtime incumbents. "You run faster if you have someone running next to you and you want to win."

All of this talk of running could make U.S. Rep. Bob Brady uncomfortable. Brady runs the Democratic City Committee - and is up for re-election next year, like everyone else in the House of Representatives. Brady declined to comment about Crowdpac or Fattah yesterday.

But state Sen. Vincent Hughes, a member of Fattah's own mini-machine, warned about targeting incumbents like Fattah, a senior member of the powerful House Appropriations Committee who has directed millions of dollars in federal funding to Philadelphia.

Crowdpac has listed Hughes as a potential challenger to Fattah, but Hughes says he's backing the congressman, legal issues notwithstanding.

"People got to be real careful about taking out a guy like that," Hughes said. "Congress works off seniority. When you get someone who's invested 10 or 20 years, and they're in there and bringing resources back, it doesn't really make sense to get rid of them."