Singling out a politician for honesty is a tough prospect.

Beyond the tribalism of America’s partisan rhetoric, there is the troubling reality of cognitive bias: try as we might, humans simply aren’t stellar at separating fact from opinion. And facts may be facts, but the conclusions we draw from those facts—for instance, what effect does the president’s party membership have on unemployment?—will tend to vary wildly.

Does one party holding the White House automatically trigger a spike in unemployment? Or is there an echo effect, where the effect of that party’s policies won’t be felt until the next administration takes over—potentially making it appear that the opposite correlation holds true?

As a result, deciphering the accuracy of claims made by politicians becomes a matter not just of comparing comments against history and fact, but of parsing the various sources behind those claims, the agenda of those providing “facts” for reference by politicians, and navigating the double-speak and malapropisms that inevitably emerge from any public (or private) comment.

The point is, honesty in politics usually turns out to be “honesty” or honesty*, followed by an abundance of qualifying footnotes. As it would happen, the PolitiFact’s Truth-O-Meter evaluates political statements using a system that obligingly leaves room for ambiguity by ranking statements as “Mostly True” or “Mostly False” or even optimistically “Half True.”

As fact-checkers go, this at least provides a quantitative basis for tracking and aggregating candidate records on the campaign trail, if not an absolute ruling on who, if anyone, is genuinely reliable as a source of fact.

That is also why, in the 2016 presidential contest, Martin O’Malley is high in the running for the Most Honest Candidate prize.

If we are to judge O’Malley based on his aggregate scores on the Truth-O-Meter, his record lands him firmly in the middle. That is, O’Malley is the most honest presidential candidate, if only because he appears to refrain from saying anything of valid substance.

Of all the major candidates, O’Malley is the only one who has managed to avoid entirely outright lies—along with outright facts. He has mastered the tightrope walk of mixing fact and opinion to the point that his comments can’t be dismissed out of hand as total bunk, yet can never be accepted on face value, either.

His one full-on “False” rating is really a matter of degrees in interpreting unemployment figures—a fuzzy practice at best, despite its popularity as the be-all and end-all metric for gauging economic health, policy success, and personal responsibility of leadership.

Excusing that aberration from the record, O’Malley stands at a whopping 56% “half true” which, by extension, means more than half of his claims are also Half False. Not only is that an absolute majority, but it is more than double any other candidate’s rate of half-truths in the entire presidential race.

If we disregard O’Malley and his miraculously level teeter-totter, then Bernie Sanders appears to emerge as the most truth-prone candidate, with the lowest rate of “False” or “Mostly False” statements (28% together) and “Pants on Fire” lies (Politifact judges him to have zero of these, although FactChecker.org is less forgiving of his exaggerations and misquotes). Taking his “Mostly True” and unambiguously “True” scores together, a 54% majority appears—though Clinton is, apparently, not far behind.

Clinton is a poster child for the difficulty of parsing public comments for factuality. Although Sanders has also had a lengthy career in politics, Clinton’s tenure has been much more visible, and since she has run for president before, she has a larger record under scrutiny than any other candidate in either leading party. Perhaps if O’Malley had a record as exhaustive as Clinton’s, his rating would tilt one way or the other, too.

For her part, Clinton’s Truth-O-Meter ranking tilts decidedly toward True, with an aggregate 51% of “True” and “Mostly True” comments on the record. Her 27% “False” or “Mostly False” is technically less than Sanders’ 28%, but Clinton also racks up a few “Pants on Fire” lies, which keep her from beating her primary Democratic challenger on this measure of honesty.

The Republican contest has kept the folks at FactCheck.org much busier than the Democrats, but then again, the GOP field is much more crowded and competitive, and has hosted far more debates. Given the opportunity, then, the Republicans have had a lot more facts and falsehoods to spread among them.

John Kasich, whose mixed polling in the primary leaves him squarely in rounding-error territory, has a much clearer record on fact-management -- with 52% “True” or “Mostly True” and just 32% in falsehood territory, he is the leading Republican candidate in PolitiFact’s metrics.

Stepping just outside the margin of error in the polls, Jeb Bush leads his party’s candidates with a 48% total score on “True” and “Mostly True” comments, with only 38% across all “False” measures. As the most tenured Republican candidate, Bush—like Clinton—also has the longest record by which to gauge his comments, making his truth score at least marginally more reliable than his current status in the polls.

The remainder of the field (or at least those ostensibly above 2% in the polls heading into Iowa and New Hampshire), in descending order of aggregate “Truth” scores (alongside their respective “Mostly False” to “Pants on Fire” totals) is as follows:

• Rand Paul: 46% true (versus 33% false)
• Chris Christie: 41% true (versus 32% false)
• Marco Rubio: 37% true (versus 40% false)
• Carly Fiorina: 26% true (versus 53% false)
• Ted Cruz: 20% true (versus 67% false)

Finally, caught up in the race to the bottom is Donald Trump, managing just 7% in “Mostly True” with no statements rated as entirely “True,” yet putting up an impressive 55% between “Mostly False” and “False,” capped off with a 21% “Pants on Fire” rating.

Ben Carson, meanwhile, scores dead last with just 4% true, against a solid 72% “Mostly False” or “False,” along with a 12% “Pants on Fire” total. So while Trump leads the field in outright lies and extraordinary fabrications, his cocktail of semi-truths keeps him above Carson’s 84% total falsehood score.