It’s an impulse as old as politics.

Supporters want to see their political champions not just as comrades in a common cause, but as the very personification of honesty and integrity.

Warning: Cognitive Dissonance Ahead. Campaign 2016 features two major-party candidates who sometimes treat the truth not as a political imperative, but rather as an expendable commodity.

Mendacity, like grandiosity, seems marbled into Donald Trump’s makeup, so much so that it’s hard to discern a true north in his characterological compass. But as we’re seeing with Hillary Clinton’s e-mail imbroglio, she, too, is willing to mislead voters when it suits her purposes.

That’s not to argue the two are equal offenders. According to the campaign watchdog PolitiFact, 50 percent of Clinton’s vetted public statements were true or mostly true, with another 21 percent half-true, while 28 percent were false or mostly false. Only 1 percent qualified as “pants-on-fire’’ whoppers.

By contrast, only 8 percent of Trump’s examined claims were true or mostly true, with another 16 percent half-true. An astonishing 57 percent were judged false or mostly false, while another 19 percent earned PolitiFact’s not-so-coveted “pants on fire’’ classification.

Clinton, then, is not a routine or regular liar, as her critics would have it.

All that said, however, when the going gets tough, Hillary, like a certain Clinton before her, has shown herself willing to lead voters in a deceptive direction. How, for example, can she have described herself as “more than ready to talk to anybody, any time,’’ as having “encouraged all of my assistants to be very forthcoming,’’ and as “happy to answer any question that anybody might have’’ about the e-mail matter, when in fact she and several of her top aides refused to be interviewed by State Department investigators conducting an internal review?

I put that question to the Clinton camp. Spokesman Brian Fallon, who underscored that Clinton has acknowledged she made a mistake in using a private e-mail server, said Clinton’s comments about cooperation referred to the Justice Department investigation, not the internal State Department effort.

“She has said that always in context of being asked about the Justice Department review,’’ he said.

But if Clinton and her team never intended to cooperate with the internal State Department assessment — something I find extraordinary, given that it’s her own former agency, and not a partisan congressional committee — she should have made that clear. Instead, her statements created the (mis)impression of complete cooperation.

Some Clinton defenders have seized on the fact that the IG’s report doesn’t allege that Clinton did anything illegal. But conduct doesn’t have to be illegal to be high-handed, objectionable, or misleading.

So does Clinton’s lack of candor here matter?

Electorally, probably not. When it comes to truth-telling shortcomings, the GOP’s presumptive nominee does her one — no, make that two or three — worse. Further, despite the concerted effort each side always makes to disqualify the other’s presumptive nominee on character issues, most people don’t and won’t vote against their favored party because its nominee occasionally sports a protracted proboscis. Instead, they just wish that unsightly appendage away.

Still, in this latest episode, Clinton has reinforced her longtime reputation as someone whose commitment to candor is something less than ironclad. All that makes it a harder slog up the hill to the high ground.

Nor should her camp be resentful if reporters occasionally treat her as though she’s on probity probation. For that, she herself is at least partly to blame.

Scot Lehigh can be reached at lehigh@globe.com. Follow him on Twitter @GlobeScotLehigh.