Has the other shoe finally dropped for Philadelphia's tottering, rust-covered Democratic "machine"? It sure looks that way. Despite years of scandal and greed tearing through the ranks of the city's one-party rulers like a killer influenza, taking down heavyweights such as State Sen. Vince Fumo, U.S. Rep. Chaka Fattah, District Attorney Seth Williams, and others lesser known, the party boss — U.S. Rep. Bob Brady — has somehow managed to surf above the bubbling cesspool.

Until now. Reports surfaced last week that federal prosecutors are investigating whether Brady's 2012 re-election campaign secretly paid a rival $90,000 to leave the race — a probe that's already secured a guilty plea from a lower-level participant — and whether Brady himself coached a witness reported to be former Mayor W. Wilson Goode Sr. Brady's lawyers insist that nothing illegal took place. Whether that assertion holds up may determine whether Brady can stay atop one of America's last urban political machines, where he has been perched since 1986.

But regardless of what any criminal probe ultimately turns up, the political ramifications of what Brady has really been up to for nearly 19 years as a U.S. congressman for central Philadelphia and blue-collar swaths of Delaware County are much larger than most people realize. In his single-minded determination to hold onto a job that offers the Democratic boss a $174,000 annual salary, supersize perks, and a lucrative future pension, with the added hurdle of doing so as a white man in a mostly nonwhite district, Brady has made "accommodations" (his favorite word) that have proved damaging to the progressive issues that his Democratic Party claims, however weakly, to stand for. Indeed, if a repeal of Obamacare ever passes the House of Representatives by a vote or two, or if Democrats fall just short in their 2018 drive to retake Congress and put a spike in President Trump's agenda, you could actually blame Bob Brady's blind ambition.

Let me explain.

As the main political writer for the Daily News in the late 1990s, I was present at the creation — the moment when Brady, who'd been the party leader for about a decade, anointed himself as the replacement for then-U.S. Rep. Tom Foglietta, who'd been named U.S. ambassador to Italy. The idea of Brady's representing the First Congressional District seemed a stretch. The Overbrook native didn't even live in the district. He'd never been elected to anything, having been trounced the one time he'd run for an at-large City Council seat. He knew next to nothing about the issues before Congress. Brady — whose selling points included a long career of working with organized labor — even told me he was unfamiliar with NAFTA, a cause celebre for unions at that time.

Politically, those weren't even his biggest problems. The First District had grown increasingly nonwhite over the years, and so for Brady to win in 1998 he would have to follow Foglietta as — at that time — the only white congressman in a majority-black district in the entire United States. But whatever Brady lacked in understanding the issues he'd be expected to vote on, he made up for in stealthy political savvy. I still remember the news conference where Lucien Blackwell — a former one-term congressman and City Council member — declared his own candidacy to replace Foglietta. With Blackwell's prominent hat in the race, other leading African American pols stayed away — which made it all the more strange when Blackwell announced he'd changed his mind and decided not to run after all. Had he iced the field to clear the way for his friend, Brady? It looked that way to many.

Still, one black elected official — a state representative from North Philly named Andrew Carn — didn't get the memo and challenged Brady in that 1998 special election. Brady, backed by every ward leader and powerful player, easily defeated Carn, and a party-endorsed candidate — Jewell Williams, now sheriff — crushed Carn in a Democratic primary for his state House seat the next time around. The Machiavellian message was loud and clear. The boss would use any combination of carrots and sticks to keep his new day job as a U.S. congressman.

As a congressman, Brady's been a mixed bag. He's good at mediating local disputes like labor strikes, terrible at passing legislation that doesn't involve renaming post offices — even though he represents a district with the highest rate of deep poverty in America. Everyone who knows Brady — myself included — agrees he's been largely a positive force on most race-related matters, most famously when he rallied balky white ward leaders behind Goode in a 1987 mayor's race where many of them had been inclined to back Frank Rizzo. Yet Brady's racial enlightenment never extended to giving a nonwhite a fair chance to defeat him in the First District.

It came to a head in 2011-12, as congressional district lines were redrawn in Pennsylvania and across the nation. Here in the Keystone State, with GOP majorities in both state houses and a Republican governor in Tom Corbett, lawmakers produced the worst partisan gerrymander anyone has ever seen. (My own Seventh District in the western suburbs, in a blatant move to improve the re-electability of GOP U.S. Rep. Pat Meehan, flaps like an insane butterfly across Southeastern Pennsylvania — a Rorschach test that Dr. Rorschach himself would have rejected as too crazy.) Critics said — correctly —- that the lines would create a huge GOP edge in Pennsylvania's congressional delegation for the 2010s and possibly beyond.

Yet one powerful state Democrat supported the gross gerrymander: U.S. Rep. Bob Brady. As was widely reported at the time, the map accomplished what may have been a long-term objective of the Philly Democratic boss: It increased the percentage of white voters in his district by adding more blue-collar river towns in Delaware County. When Republicans — because of an unusual intramural spat — needed Democratic votes to pass their map, Brady made the phone calls to make sure they got the support they needed.

The end result was — and this seems to be a theme here — to thwart the will of the people. Even though the Democratic Party actually has a slight registration edge in the state, GOP dominance of the 18-member congressional delegation is currently 13-5. Were it not for extreme gerrymandering, an in-depth analysis by the Associated Press found, the gap would be only 10-8. In a highly divided Congress, with life-or-death issues such as the future of Obamacare on a razor's edge, those three votes may ultimately prove a big deal.

Why didn't someone call Brady on this back in 2012? Some people did. One high-ranking pol called the move, in an open letter to Brady, "precisely the sort of self-serving backroom maneuver that is destroying confidence in our political process." The author of that scathing letter was Municipal Court Judge Jimmie Moore, the man who was preparing to challenge Brady in a primary and then dropped out just seven weeks after his letter — amid, as we've just now learned, five years after the fact, another "backroom maneuver" that has become the subject of a criminal investigation.

It's all connected — the endemic corruption in the Philadelphia Democratic Party, the cynical deals like the 2012 gerrymander, and citizens' massive dissatisfaction with their government. In the last few years, we've seen thousands of Philadelphians take to the streets again and again to plead for a living wage, to protest police shootings, to beg for stronger action to thwart an increasingly despotic president. And much of the local political establishment struggles to respond —- because it doesn't even know how to conduct the people's business. It's only a job-protection racket, straight up, with Bob Brady at the top. The time for Brady to step aside, for a new generation of people who actually care, was years ago. But history has taught us that the boss will fight to prevent that from happening, by any means necessary.