One of the first questions Senator Bernie Sanders faced after launching his presidential candidacy last week gave him an opportunity to draw a contrast between himself and Hillary Clinton: Will the Clinton Foundation’s fundraising practices be “fair game” in his campaign?

Without any hesitation, Sanders called it a “fair issue,” but he didn’t take the bait. He went after a different target instead.

“I think what is more fair game for my campaign is the role of money in politics, alright? Where are the conflicts of interest when the Koch brothers are going to be spending $900 million in this campaign, making a lot of their money from fossil fuel and having a platform which as I understand it calls for the elimination of Social Security, Medicare and Medicaid, ideas which are increasingly palatable to my Republican colleagues. Do you think that’s a conflict of interest?”

If you take a cynical view of politics, you might wonder whether Sanders calculated his pivot from the question of Hillary Clinton’s official conflicts of interest to an answer about billionaire Republican donors. Sanders is the darkest of dark horses. His candidacy is widely viewed as an instrument designed to make Hillary Clinton’s campaign—the heavily favored, establishment campaign—more progressive. That’s not only because Sanders is an exotic political creature, but because he more or less admitted as much a year and a half ago, when he told the Washington Post, “I don’t wake up every morning saying, ‘Oh my goodness, I really want to be president.’ But somebody’s got to be out there, and if nobody is, I’ll do it.” If the goal is to push Clinton in the right substantive direction, rather than to defeat her, then declining to attack her character or ethics has a perfect logic to it. Don’t weaken Hillary. Strengthen her.

But there’s a simple reason to believe Sanders’s answer wasn’t calculated at all, let alone to run interference for his supposed rival. As much as it sounded like deflection, Sanders was actually asking an incredibly apt question—one which I suspect will make it difficult for Republicans to exploit the conflict-of-interest questions swirling around the Clinton campaign.

The corruption story propounded by Clinton’s critics is unfalsifiable: Connect the dots between Bill Clinton’s funders and paymasters, and various policies the State Department adopted under Hillary Clinton’s leadership, as the New York Times and other news outlets have done; pepper the conflict of interest story with innuendo about her email record-keeping protocols during that time; and you have the outline of a juicy pay-to-play scandal. Powerful people and governments gave Bill and the Clinton Foundation money over the years. Many of them had interests before the State Department. Some of them benefited from State Department policy. And to the extent that no evidence exists showing that Hillary Clinton directed that policy on behalf of her husband’s donors and solicitors, you can chalk it up to the fact that she probably deleted it.

It’s a plausible story in a “Whoa, if true!” kind of way, and it doesn’t wear well on her, even if the policy decisions themselves are defensible on the merits. Writing at The Week, Michael Brendan Dougherty predicts that Clinton’s campaign is “going to be an unpleasant slog for liberals.”

“[D]efending Hillary Clinton,” Dougherty continues, “will require constant mental effort to say that thus-and-so only looks bad, or to note that others engage in pay-to-play graft, too. It's going to be exhausting and demoralizing.”

There’s some truth to his argument, which harks back to her pre-candidacy days when liberals would read aghast all the stories about Clinton giving paid speech after paid speech to questionable interests. But it only goes so far.

A political scandal can’t easily come to define a candidate without the consistent patter of revelation after revelation, dribbling forth from the press, until that candidate’s identity is covered over. For that to happen now, Hillary Clinton’s political nemeses would have to play an active role in building a narrative about her and they can’t easily do that unless their hands are clean. Loaded questions are the lifeblood of antagonistic politics, but they lose effect if they can be turned on the questioner. Sanders’s answer to the Clinton Foundation question underlines how Clinton can turn conflict-of-interest innuendo around on her Republican rivals, almost to a person.

Unlike Ted Cruz, the Republican Senator from Texas who had four different families contribute to super PACs that will help him, Mr. Bush has gone about the fund-raising for the Right to Rise super PAC in a traditional fashion. He’s held a staggering number of fund-raising events since the beginning of the year.

Mr. Bush’s financial edge is somewhat less significant in an era in which people like Mr. Cruz and Senator Marco Rubio of Florida are able to raise substantial sums from single donors. But, even if the money does not guarantee that Mr. Bush will be the nominee, it will give him enough to last through a protracted nomination fight.

Speaking as one of the aforementioned aghast liberals, this isn’t intended as a tu quoque defense of Clinton’s activities. It’s a question of basic political mechanics. Will any of Hillary Clinton’s potential rivals be able to criticize her over questionable donors, without exposing themselves? Clinton can respond with pride in the work the Clinton Foundation has done, mostly with money from disclosed donors, whereas Republican donors aren’t giving to charity—they’re trying to curry favor with the next president. In more than one case they have helped to elect these presidential hopefuls to prior public service jobs. And nobody knows who they are.