When a smug political machine sends dutiful functionaries to Harrisburg whose chief responsibilities are to back the party, vote as instructed when instructed, and collect a paycheck, it should come as no surprise when arrests occur.

Democratic State Reps. Louise Bishop, Michelle Brownlee, Ronald Waters, and Vanessa Lowery Brown, all of Philadelphia, didn't have the decency to resign after The Inquirer reported in March 2014 that they had been recorded taking cash from an undercover informant in a sting conducted by the state Attorney General's Office.

They knew they had done something wrong; all but Bishop admitted as much to a grand jury. The city Democratic Party knew they had done something wrong, too, but it shamelessly supported their reelection. Only Brown drew challengers.

Attorney General Kathleen Kane declined to make any arrests despite evidence collected in the sting, declaring the cases tainted and unprosecutable. But Philadelphia District Attorney Seth Williams, goaded by Kane, picked up the investigation and proved otherwise. Charges were filed last year against Waters, Brown, and former Traffic Court Judge Thomasine Tynes, who pleaded guilty to a conflict-of-interest charge and has been sentenced to up to 23 months in prison. This week, charges were filed against Bishop, Brownlee, and ex-State Rep. Harold James, a former Philadelphia police officer who left the legislature in 2012. James was allegedly recorded taking cash and asking what he could do for the informant.

Six Democrats have been accused of taking money and gifts from an individual who was obviously trying to put himself in a position to ask them for favors, and their party acts as if it's no big deal. Democratic leaders say they care about Philadelphia, but they perpetuate a one-party system in which unproductive politicians who are susceptible to bribery get elected and reelected over and over again.

It's as if city Democrats are practicing a political form of omertà, the term mobsters use to refer to the code of silence within criminal organizations. They, too, keep their mouths shut when asked about illegal behavior.

U.S. Rep. Bob Brady, who heads the city Democrats, undercuts his legacy by not leading the party in a different direction. Other leading Democrats - including Mayor Nutter, City Council President Darrell Clarke, State Sen. Vincent Hughes, U.S. Rep. Brendan Boyle, and union leader John Dougherty - should be pushing for an injection of new blood into the party so it can stop offering voters the same sorry cast of characters on every ballot.

The moribund Republican Party deserves criticism as well for failing to offer viable alternatives. The Democratic Party's consequent dominance has drowned out the diversity of voices and views needed to make the city a more vibrant place to live.

It would be ludicrous to think there aren't more sincere, intelligent, honest, capable people in the West Philadelphia districts represented by the politicians now accused of crimes. Some are trying to improve their city in other ways. But the city needs them to run for office even if the Democratic Party doesn't agree.