Another one bites the dust.

Pennsylvania is no stranger to corrupt politicians, but it’s especially discouraging to see Philadelphia District Attorney Seth Williams plead guilty to corruption charges.

Without warning Wednesday, 10 days into his federal trial on 29 charges, Williams pleaded guilty to a single charge of accepting a bribe. His immediate resignation was a condition of the plea agreement.

There had been high hopes that Williams might be the political reformer that’s so badly needed in Pennsylvania — particularly in Philadelphia. He had emerged as something of a hero during the scandal we once knew as Kathleen Kane.

Williams was widely perceived as the righteous opponent of then-Attorney General Kane. In 2014, Kane, a Democrat, shut down a sting operation and chose not to prosecute Philadelphia judges and state lawmakers who had been secretly recorded taking cash and gifts. She said the sting unfairly targeted blacks. Williams — who is black and also a Democrat — picked up the cases and won several convictions.

Kane subsequently was convicted of perjury and obstruction of justice. She remains free on bail while appealing her conviction and sentencing.

Williams’ guilty plea reveals that even while he appeared to be battling political corruption at the state and local level, he himself was wallowing in it. Prosecution witnesses told of cash gifts given to Williams to fuel a lavish lifestyle, and how Williams used government vehicles as if they were his own. He was accused of misappropriating campaign funds for personal use.

And voters are, for the most part, indifferent. On March 24, just three days after Williams was indicted, there was a special election for a vacant State House seat. Voter turnout was less than 5 percent; even so, the outcome was considered questionable and is under investigation for possible campaign fraud. For those keeping score, that’s 95 percent of the electorate not showing up, and the 5 percent who do, not being trusted.

The looming question: Is the political system so much controlled by favors and bribes that it will never change?

Offhand, you might say the answer is criminal convictions. But Pennsylvania has a long and growing list of convicted former officials. Seth Williams is only the latest inductee in the cavernous Keystone Hall of Shame. It doesn’t seem to matter.

Stiffer punishments might be the answer. But how likely are lawmakers to impose tougher consequences on themselves for sins they assure us they’d never commit — especially as they weigh the influence of campaign contributions against an electoral turnout as low as 5 percent?

If the Kathleen Kane scandal raised any hope, it was that someone like Seth Williams might turn out to be a solid public servant — one who put the electorate ahead of the lobbyists, political parties and himself. We were sadly mistaken.