On a debate stage that features a former vice president and two of America’s best-known progressive leaders, even a billionaire can have a hard time standing out.

But, as the US political world debated what could possibly have been said off-mic by Elizabeth Warren and Bernie Sanders after their tiff just an hour earlier during the Tuesday Democratic debate, businessman Tom Steyer managed to find his own breakout moment: People noticed that he had drawn something on his hand.

As it turns out, the billionaire has been marking his left hand with that same symbol now for a couple of years — a hand-drawn cross with four more crosses in each quadrant.

And, while Mr Steyer — a longtime Democratic donor — is himself Christian, it turns out his motivation is even simpler than that. He does it to remind himself to stay honest, he has said.

Here’s what you need to know about the markings on the long-shot presidential candidate’s hand.

The symbol is known as the Jerusalem Cross, or the Crusader’s Cross

The cross is perhaps best known for its use during the 13th Century, when it was displayed for the Kingdom of Jerusalem, which was established by European Christian crusaders who conquered Muslim lands.

The cross was used before then, as well, and was apparently used in feudal states in the country that is now Georgia. It has been on that country’s flag since 2004.

Its meaning is disputed

Some claim that the five crosses represent Jesus Christ and the four gospels. Others claim they represent the five wounds Christ is said to have sustained while on the cross. Still others say it represents the four points of the compass.

In the context of Christian pilgrimage to Jerusalem, though, the symbol is generally seen as one of peaceful worship.

Which explanation does Mr Steyer subscribe to?

Mr Steyer, who is himself Christian, has used it for a somewhat more secular reason.

During an interview last year with Buzzfeed News — before his presidential bid was launched — Mr Steyer said it had to do with being honest.

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“It means to tell the truth no matter what the cost is,” Mr Steyer said. “For a while now, I have drawn it on my hand every day to remind myself to always tell the truth. I later discovered that it has traditionally been known as a Jerusalem cross.”

He has also provided a similar answer during an interview with Politico, and has indicated he started drawing it on his hand after he launched the group Need to Impeach in 2017, to try and keep himself honest.

There are other modern interpretations, too

As the BBC reports, the Crusades in the Middle East have been tied in recent years to the rise of white supremacists, and the Jerusalem Cross has been a part of that imagery.

Just last year, for instance, a white supremacist who shot 50 people dead in Christchurch in New Zealand reportedly had references to the Crusades in his so-called manifesto.

Crusades references were also observed at the far-right rally in Charlottesville, Virginia, in 2017.