PolitiFact presents itself as a nonpartisan truth umpire, but here’s the story behind how its metrics are biased against Republicans and highly attuned to political winds.

In the last article, we that showed top fact-checking website PolitiFact generally rates Republicans as less honest than Democrats and their style betrays the need to constantly explain why Republican statements that seem true are actually false. While this approach gives us some insight into how PolitiFact skews against Republicans, another important component is which facts they choose to check.

It is extremely hard to pin down exactly which facts PolitiFact declines to check. We could argue all day about individual articles, but how do you show bias in which statements they choose to evaluate? How do you look at the facts that weren’t checked?

Our first stab at this question came from asking which lies each candidate was famous for and checking to see how PolitiFact evaluated them. These are necessarily going to be somewhat subjective, but even so the results were instructive. With Donald Trump, we discovered the lies that were best-known were usually checked and frequently re-checked later on. All but one was marked as “False” or “Pants on Fire”.

Donald Trump’s Top 5 Lies

1. Claiming He Did Not Support the Iraq War

6 Checks: Mostly False False, False, False, False, False.

PolitiFact checked this. And checked it and checked it and, just in case they missed something, they checked it again. Then they checked it.

They checked Trump’s exact statement six separate times, finding it false each time. Keep in mind that PolitiFact frequently points back to the sum total of all their checks when determining which politician is more or less truthful, so this lie is counted as six separate falsehoods.

2. Claims about President Obama’s Birth Certificate

8 Checks: False, False, False, False, False, Pants on Fire!, Full Flop.

Politifact checked Trump on issues related to President Obama’s birth certificate a total of eight times. The checked four times on whether Hillary Clinton had anything to do with starting the birther rumor, two times on statements that were skeptical of Obama’s birth status, once on whether he brought the issue to a close and, finally, a “Full Flop” rating when Trump admitted that Obama was born in Hawaii.

3. Claiming He Had No Relationship With Vladimir Putin

1 Check: Full Flop.

PolitiFact checked this and rated it as a “Full Flop” (Trump said it, then claimed he never said it).

4. Claims of Large-Scale Voter Fraud

5 Checks: Pants on Fire!, Pants on Fire!, Pants on Fire!, Pants on Fire!, Pants on Fire!

PolitiFact rated Trump’s claim that there was large-scale voter fraud on and before Election Day as “Pants on Fire.” We tried to limit this to this very specific claim. Trump made several other statements related to the idea of voter fraud that were also checked and found to be false.

5. Claimed Hillary Would Let 650 Million Immigrants In

1 Check: Pants on Fire!

PolitiFact checked this claim (which wandered between 600 million and 650 million) and found it to be “Pants on Fire.”

Hillary Clinton’s Top 5 Lies

The Hillary Clinton PolitiFact story was far stranger than we anticipated. Not only does PolitiFact not check Clinton as frequently, but they also often fact-check her by proxy. Strange as it may seem, PolitiFact would often look at someone talking about a Clinton statement and then fact-check the person talking about Clinton’s statement instead of fact-checking Clinton on the statement she made.

Of these five statements, PolitiFact checked Hillary four times and did two “fact checks by proxy,” compared to the 21 fact checks of Trump’s five statements.

1. Claimed She Didn’t Send Classified Emails

2 Checks and 1 “Check by Proxy”: Checked David Cicilline – Half True, False, Mostly True.

Clinton stated repeatedly that she did not send any classified emails. PolitiFact checked this a few times as the story unfolded and gave it a variety of ratings.

Their first rating was when they fact-checked not Clinton, but Rep. David Cicilline saying that the former secretary of state claimed she didn’t send any classified emails. They rated Cicilline’s claim “Half True.” Nine months later, they would rate Clinton’s statement that she didn’t receive or send classified info as “False.” Two months later, they took her claim that the emails didn’t have classified headers and rated it “Mostly True.”

2. Claim She Landed in Bosnia Under Sniper Fire

1 Check: Pants On Fire!

PolitiFact checked Clinton on this claim during the 2008 presidential primary and rated it “Pants on Fire.”

3. Claimed She Was in New York City on 9/11

Not Checked.

We did not find any PolitiFact fact check on this statement.

4. Claimed the FBI Was Fine with Her Email Use

1 Check: Pants on Fire!

PolitiFact checked Clinton on this claim in August and rated it “Pants on Fire.”

5. Claim She was Named After Sir Edmund Hillary

1 “Check by Proxy”: Sen. Mitch McConnell, rated “Half True.”

PolitiFact did check this statement, but only by proxy. Senate Majority Leader Mitch McConnell noted that Clinton has a history of lying and included her statement that she was named after Sir Edmund Hillary. PolitiFact verified that he was correct, but proposed that it is possible a young Hillary’s parents lied to her about it. Because they could not verify that this was an intentional lie, they rated McConnell’s statement as “Half True.”

The simplest explanation for the disparity in lies checked between Trump and Clinton is that when Hillary gets caught in a lie, she stops lying, while Trump continues lying.

This is not something the evidence seems to support. Barack Obama continues to this day to claim that women make 77 cents on the dollar compared to men. PolitiFact rated this as “Mostly False” in 2012, but changed their rating to “Mostly True” when Obama made the same statement in the State of the Union but with fewer details. Their excuse was that Obama’s claim was misleading but technically true if you look at data with the least possible context. (This is a standard PolitiFact prefers for Democrats but abhors applying to Republicans.) Obama (and most Democrats) continue to this day to make this incredibly misleading claim.

Yet Mitt Romney was checked five times (each one rated false) for making the arguably true statement that Obama apologized for the United States when visiting foreign countries after being elected in 2008. PolitiFact found Romney was right that Obama expressed regret over recent U.S. policy, then proceeded to go on a 3,000-word diatribe about what exactly constitutes an “apology.”

The pattern is there: PolitiFact checks Republicans repeatedly for the same facts, especially if they feel they can rate them “false.” Keep in mind that PolitiFact routinely touts its aggregate truth ratings, so running up the “false” scoreboard on Republicans matters when they release their “who is more honest” data stories.

Even so, this review of candidate lies suffers from the fact that we have to, by necessity, pick and choose the facts to review and look individually to see if PolitiFact has checked them. It would be instructive to see how often PolitiFact chooses to fact-check individual politicians. Let’s take the fascinating case of Sen. Marco Rubio.

Is a Senate Candidate More Important Than the House Speaker?

Rubio was the junior senator from Florida for nearly six years before coming in third place in the 2016 Republican primary. Yet PolitiFact was checking him nearly every month since a year before he was elected to the Senate.

Rubio was fact-checked as many times before he took office than long-time senator and erstwhile Senate Majority Leader Harry Reid has been checked in his entire career. Before he even started his presidential campaign Rubio was fact-checked 10 times more Democrat Sen. Elizabeth Warren has been during her tenure.

Below is a segmentation of fact checks for Clinton, Rubio, and Reid, showing where in their careers PolitiFact has checked their statements.

Before he even announced his run for president, PolitiFact had checked Rubio more times (87 fact-checks) than they had checked Clinton during her entire 2008 presidential run (83 fact-checks). It seems over-eager to check a four-year junior senator more than a presidential candidate, vice president, Senate majority leader, and speaker of the House.

Nor was Rubio alone in this. Before he ran for president, Sen. Ted Cruz was fact-checked 46 times, more than any Democratic senator we checked. House Speaker Paul Ryan was fact-checked nearly twice as often as former House Speaker Nancy Pelosi, even if you take out every single fact check from the time period in which he was the Republican vice presidential nominee. Michelle Bachmann (remember her? Three-term congresswoman who placed sixth in the Iowa caucus) was fact-checked a stunning 51 times, nearly as many times as governor, senator, and vice presidential candidate Tim Kaine.

This would of course be a difficult metric to keep track of on a case-by-case basis, which is how fact-checking is done. But it is clear from the numbers that PolitiFact will, especially in off-election years, seek out a speech from a prominent Republican delivered at a conference or assembly and select a fact from the speech that they feel is inaccurate.

Donald Trump, the Democrat

One thing you may have noticed through this series is that the charts and data we’ve culled show a stark delineation between how PolitiFact treats Republicans versus Democrats. The major exceptions to the rules we’ve identified in PolitiFact ratings and analytics have been Trump and Vice President-elect Mike Pence. These exceptions seem important. After all, who could more exemplify the Republican Party than the incoming president and vice president elect?

It should be noted that all this data scraping and analysis was done before the election. As we planned this series, we were anticipating a deep dive into Hillary Clinton’s record, contrasting it with that of major Republicans. But Clinton suddenly appears less important than President-elect Trump.

Trump threw a wrench into my analysis. Here I was, with a fairly clean story about PolitiFact being particularly unfair to Republicans, rating them more harshly, unfairly calling them liars with alarming frequency. Then along comes a candidate who seems to take a more … um… “casual” approach to the truth, and who is easy to fact-check because his statements are so careless and brazen, and his every statement is spread across the world so quickly.

Now, while I’m talking about Trump in this article, most of the same things can be said about Pence. Pence has spent an enormous amount of time reinforcing or defending statements that Trump has made and most of Pence’s fact-checks are based on statements he made as Trump’s VP choice. As a result, PolitiFact rates Pence the third most “dishonest” Republican we checked.

“Only the third?” you may ask. “Who was in between Trump and Pence?” I’m so very glad you asked. The second most “dishonest” politician PolitiFact rated was Cruz. Let’s compare Cruz to Trump.

Trump Versus Cruz All Over Again

Note: For truth ratings, we used the following metric: True = 0, Mostly True = 1, Half True = 2, Mostly False = 3, False = 4, Pants on Fire = 5. This means that lower scores are “more truthful.” The higher a politician’s “truth score” is, the more PolitiFact has called him a liar.

In total truth ratings, Trump’s average rating was 3.2, slightly worse than “Mostly False” as an average. Cruz’s average rating was 2.8, slightly better than “Mostly False.” If we look at the truth values over the course of the primary, a couple things stand out:

We see that Cruz was rated as significantly more truthful than Trump in two months, August and November 2015. Cruz was fact-checked twice in August and thrice in November, while Trump was fact-checked a total of 23 times those two months. (Cruz was not fact-checked in June, when Trump announced his nomination.)

During the most important months of the primary campaign (December 2015 and January 2016) PolitiFact checked Cruz more frequently than Trump and became substantially harder on Cruz, rating him at nearly the same level of dishonesty as Trump. In the months following, the ratings of both candidates improved at about the same rate. Until Cruz withdrew from the race.

In the month after Cruz dropped out of the race, PolitiFact unleashed on Trump with five “Pants on Fire,” five “False,” three “Mostly False,” and one “Half True.” Before he clinched the nomination, Trump was portrayed as just a slightly more dishonest GOP candidate. After the nomination, he was portrayed as a flat-out liar.

Explaining Away Ted Cruz

Things get more interesting when we look at the nature of these fact-checks. We looked earlier at how longer fact-checks indicate PolitiFact feels the need to explain themselves in defending a rating that may be questionable. When we look at the word counts for Trump against almost any other Republican, Trump’s word counts do not fit with the pattern for Republicans, but the one for Democrats.

Articles calling Cruz a liar (“Mostly False,” “False,” or “Pants on Fire”) are 30 to 40 percent longer than the same ratings for Trump. This means that, while PolitiFact was comfortable giving the overall ratings impression that Cruz and Trump were both liars cut from the same cloth, they consistently felt the need to explain at length why Cruz was a liar (a pattern we see with nearly all Republicans).

In contrast, they treated Trump as a Democrat: When he lies, they state the facts plainly and let the matter rest.

PolitiFact’s Crying Wolf Syndrome

In this context, PolitiFact’s analysis of Trump reinforces the idea that the media has called Republicans liars for so long and with such frequency the charge has lost it sting. PolitiFact treated Mitt Romney as a serial liar, fraud, and cheat. They attacked Rubio, Cruz, and Ryan frequently and often unfairly.

But they treated Trump like they do Democrats: their fact-checking was short, clean, and to the point. It dealt only with the facts at hand and sourced those facts as simply as possible. In short, they treated him like a Democrat who isn’t very careful with the truth.

Unfortunately, it requires an in-depth analysis of their work to discover this. If you look only at the ratings in aggregate, the metric that they’ve used to build their brand and to slander Republicans for almost a decade, it looks like Donald Trump is just another Republican.