On Sunday, the three remaining Democratic presidential contenders will star in their fourth debate of the season, this time in South Carolina. With Hillary Clinton and Bernie Sanders neck-and-neck in early voting states, this debate could play a key role in convincing undecided Democrats which candidate to support. Depending on how things go, this could be a good thing for the Socialist from Vermont. Sanders’ debate answers have made him more trustworthy than ever in the eyes of Democratic primary voters, and that’s probably one reason his support has risen.

The stakes are higher in this debate than in the last few. Sanders has retaken the lead from Clinton in the early primary state of New Hampshire, and he’s creeping up on her in Iowa, too. As a result, this could be a more heated and contentious debate than the past few Democratic forums, which have been civil (except for when Martin O’Malley makes a desperate play for relevance, of course).

In past debates, Sanders has shown a propensity to answer questions in a way that don’t obviously or directly help his political prospects. He passes on easy political attacks, for example, and stands by less popular positions. Counterintuitively, this tactic has actually made him appear more trustworthy, not less. Here’s how he’s done it:

He Gave Hillary A Pass On The Email Scandal

When the politically-sensitive subject of Hillary Clinton’s emails came up at the first Democratic debate, Sanders was given an easy opportunity to criticize her. Instead, he said that “the American people are sick and tired of hearing about your damn emails,” and asked to move on to more substantive issues. It would have been in Sanders’ political interest to try and smear Hillary over the emails, as that could have eroded her support. Instead, he took the high road.

He Explains His Gun Policies In Crude Political Terms

Sanders has a more pro-gun record than any of the other Democrats running for president. What’s notable is that he justifies this in crude, honest political terms, explaining that he represents a state with high levels of gun ownership and needs to please those gun owners in order to get reelected. Like it or not, pandering to your constituents is a requirement for anyone hoping to be successful in politics, and Sanders is one of the few politicians to admit that he does it.

He Apologized For The DNC Data Breach

When the Datagate scandal broke just days before the third Democratic debate, the stage was set for a nasty fight between Clinton and Sanders. Instead, both of them acted graciously, with Sanders looking Clinton in the eye and apologizing for the actions of his staff. Again, this may not have pleased Sanders’ supporters, but it was the honest and right thing to do, because Clinton deserved an apology. Admitting when you've messed up is a crucial component to building trust, and that’s exactly what Sanders did.

He Says Politically Unpopular Things About Climate Change

It’s safe for a politician to say that terrorism exist because some people just hate America and want to destroy it. It’s much more politically risky to cite climate change as a key accelerant of terrorism. It's a factually-accurate claim, but one that's nonetheless mocked by many people who, um, haven’t done their research. But Sanders frequently asserts a connection between climate change and terrorism, and when asked to stand by that position at a debate, he replied that he “absolutely” does. Again, that's a risky move — which is why it come across as honest.

He’s Displayed Knowledge Of Issues That Aren’t His Specialty

It’s no secret that Sanders is primarily animated by issues of income inequality. But there are many other arenas of policy that a president must address, and knowing how to rectify disparate wealth stratification has little bearing on, say, ending the Syrian civil war. But Sanders has shown at the debates that he knows quite a bit about foreign policy. In speaking about Syria, for example, he points out that the many rebel groups fighting Bashar al-Assad, including ISIS, are often at war with each other, too. That kind of nuance is essential in crafting a smart foreign policy, and Sanders has shown that he can think in a nuanced way about things other than wealth inequality.