When we conducted an informal survey last year asking people when it’s okay to tell a white lie, a large majority, 71%, came down hard on politicians, saying it’s wrong for them to shade the truth, even when it’s just a matter of emphasizing facts that support their point of view and ignoring those that don’t.

But lying by politicians remains rampant.

Politifact.com, the premier fact-checking site of the Tampa Bay Times, regularly tests the statements of politicians against the facts to disappointing results. When I checked today, there were 20 statements on Politifact’s homepage and half were rated as false, including six that got the egregious “pants on fire rating.” All 10 of the lies on today’s page were told by Republicans, but both parties tell their share of falsehoods. On Sunday, Glen Kessler, The Washington Post fact-checker, gave President Obama the maximum four-Pinocchio rating for claiming that Republicans in Congress filibustered 500 pieces of legislation that would have helped the middle class.

The lies do not go unnoticed. In polls both here and abroad, survey respondents rated politicians as more likely to lie than any other professional group. And in Gallup’s annual survey asking which professions are ethical and trustworthy, members of Congress regularly score below 10%.

So why do politicians continue to lie even when the public disapproves so much? An article in Psychology Today cited six reasons, including that core followers will believe anything their favorite politicians say and that if a lie is repeated often enough, people will eventually believe it regardless of the facts.

So what can we do about it? The fact-checking services are an important first step. There is at least one study that shows politicians are somewhat less likely to lie if warned in advance that fact-checkers are on the case. But in this day of social media and partisan broadcasting, it’s pretty easy for politicians to bypass the traditional media. And the fact-checkers can’t do the job of everyday reporters, who need to do more than just repeat the statements they hear. The New York Times took considerable flak this week, to cite one case, because a reporter merely repeated opposing claims about voter ID laws without citing evidence that shows which claim has more validity.

The obvious solution is anything but easy. We have to make it clear to politicians that we expect the truth, that with the help of good journalism we’ll expose the fabrications, and that we’ll punish the liars when elections roll around. It’s a bit trite to say that democracy can’t thrive without a healthy discourse that’s based on honesty. But that’s a truism that ought to be enforced.