I wasn’t surprised when a federal jury last week convicted former Massachusetts House Speaker Sal DiMasi on seven of nine criminal charges.

I didn’t spend a single moment in the courtroom, but I’ve been reading about DiMasi’s legal troubles since early 2008, when the Boston Globe’s Andrea Estes broke the news that federal prosecutors had the veteran lawmaker in their sights. At trial, the government’s case against DiMasi seemed about as open and shut as they come; DiMasi’s defense team was utterly unable to challenge documentary evidence and witness testimony that their client took kickbacks from a software company in exchange for help securing lucrative state contracts.

Even after the verdict, as DiMasi faced reporters, he was unable to offer a compelling alternative narrative, only a vague legal analysis amounting to a weak syllogism: “This is an intent crime, and I knew I did not have the requisite intent to commit this crime.”

In the face of testimony by DiMasi’s former law partner, Steven Topazio, about the flow of $65,000 from software company Cognos to DiMasi—testimony bolstered by copies of the checks—the remark about “intent” seemed desperate at best. That sense of desperation, coming from a 65-year-old man who may spend the rest of his life behind bars, struck a nerve in me that neither the facts of the case, nor the longer story of corruption in high places, could touch.

Clearly, in a nation seemingly overflowing with scandal-ridden pols—to be fair, I don’t place the tawdry sex sagas of Anthony Weiner, Eliot Spitzer and Arnold Schwarzenegger in the same category as the ethics violations of Charles Rangel, James Traficant and Tom DeLay—DiMasi’s crimes aren’t at all shocking. Sadly, coming in the wake of criminal convictions of ex-state senator Dianne Wilkerson (in 2008) and ex-Boston city councilor Chuck Turner (in 2010), both on extortion charges, DiMasi’s misconduct isn’t an anomaly, but part of a pattern. As every news story about DiMasi last week noted, he is the third consecutive Massachusetts House speaker to be indicted in federal court, following Charlie Flaherty and Tom Finneran, both of whom reached plea agreements with the government rather than stand trial.

Maybe this is what happens to middle-aged reporters who’ve seen so much misbehavior from national, state and local pols that they can’t be shocked anymore: instead of taking comfort in the idea that, at least in the DiMasi case, the system—the dogged reporting of the Globe’s Estes, anyway, and the legal talents of prosecutor Carmen Ortiz—seemed to work, I’m left wondering about all the people who assisted DiMasi, directly and indirectly, in his unethical conduct. DiMasi’s crimes, and the arrogance that appears to have informed them, are part of a culture in which pols and their partisans defend all sorts of dishonesty and, as evidence of their sophisticated sense of “real” politics, the to-the-victor-belong-the-spoils mentality.

Surely DiMasi’s former colleagues on Beacon Hill—particularly those now in leadership, including House speaker Robert DeLeo, (think Probation Department patronage scandal) and Senate president Therese Murray (a top beneficiary of casino largesse), who refuse to acknowledge the depth of the ethics problem on Beacon Hill—are part of the problem.

Murray’s statement following DiMasi’s conviction is nothing more than the canned response to every scandal: “The actions of one person should not cast a shadow on the dedicated public servants in the Legislature and all their good work.” She might as well have said, “In a General Court whose leaders take thousands from casino lobbyists at the same time they advance the interests of the casino industry, it’s unfair to conflate convicted felons with run-of-the-mill hacks.”

In calling DiMasi an “outlier,” Gov. Deval Patrick (think Marion Walsh scandal, among many) similarly circles the wagons with the one-bad-apple argument. Alas, in responding to the DiMasi conviction, the state’s three most powerful politicians each chose to ignore the broader culture in which DiMasi acted; in doing so, each revealed their dishonesty, their stupidity, or both.

That leaves you and me to wonder who, if anyone, in public office we can trust.

I don’t think we should let DiMasi off the hook, though ultimately that’s for judges and juries to decide. In the court of public opinion, his misdeeds should be judged not in isolation, but in light of the culture of which he was a part. We should wonder what makes a man like DiMasi, a working-class hero from Boston’s North End, so desperate for cash, so broke and greedy and entitled, that he would risk even his freedom, let alone his dignity and good name, for filthy lucre.

Even after he’s betrayed our trust, we should wonder if we aren’t better off because of him— a consummate backroom pol, perhaps, but one who seemed for most of his career to use his power for the benefit of his working-class constituents, most of whom were far more conservative than DiMasi, a longtime supporter of gay rights. Were it not for DiMasi, the state would likely have legalized gambling and banned gay marriage.

Most of all, we should wonder: did we really get the bad apple, or just the one we were offered?