Candidates tussled over immigration, welfare, Planned Parenthood and more during the CBS Republican presidential primary debate in Greenville, S.C. Here are key moments from that debate. (Sarah Parnass/The Washington Post)

Watch almost any hockey fight, and you’ll notice a referee standing off to the side, watching — making no attempt to break things up. He’ll let the combatants trade blows for a while, tire themselves out a bit, then finally step in. It’s part of the spectacle of a hockey game, after all.

CBS moderator John Dickerson did his best impression of a hockey ref on Saturday night when a Republican presidential debate in Greenville, S.C., got rowdy. The candidates dropped the gloves repeatedly, and Dickerson let them go at it.

“You are the single biggest liar,” Donald Trump said to Ted Cruz after the Texas senator asserted that “most of [Trump’s] life, his policies have been very, very liberal.” Back and forth they went from there — “Donald has this weird pattern”; “that’s a bunch of lies” — with Dickerson merely spectating.

At last, Dickerson interjected: “Hold on, gentleman. I'm going to turn this car around.”

Another time, Marco Rubio threw a jab at Cruz, pointing out that the senator who shares his Cuban heritage “doesn’t speak Spanish.” That remark ignited a heated exchange on immigration, which went on at length before CBS’s Major Garrett, a panelist for the debate, interrupted to direct a question to Jeb Bush.

After halting Cruz to correct a factual error early in the night — and apologizing for doing so — Dickerson seemed reluctant to force his way in during the rest of the debate. There were moments when he appeared to be on the verge of losing control; in fact, he said “we’re in danger of driving this into the dirt” at the end of the Trump-Cruz scuffle.

But, for the most part, Dickerson and his panelists were wise to recede into the background for long stretches. Watching the candidates duke it out with no need for goading, I was reminded of how hard previous moderators had to work to draw out the differences among rivals who often wanted to just agree and get along.

In December, I applauded CNN debate panelist Hugh Hewitt for pressing to reveal a split between Cruz and Trump, who had carried on quite the bromance to that point. But Hewitt’s heavy hand wasn’t inherently better than Dickerson’s light touch — it was simply what was required at that stage of the race to expose distinctions. Which, after all, is what a debate is about.

When the candidates come ready to disagree — vehemently — as they did on Saturday, the moderator can assume a more passive role. And with the field considerably smaller (down to six from a high of 11 at the fourth GOP debate), Dickerson could let repartees go on longer without totally trampling other candidates’ speaking times.

Yes, there were moments when feuds got personal, and Dickerson could have done more to compel the candidates to stick to policy. But on the whole, I’d take a less-involved moderator as a good sign that the race is intensifying and the remaining contenders are ready to separate themselves.

Debates are better when moderators don’t have to manufacture conflict. On Saturday in South Carolina, the Republican presidential candidates created plenty on their own.

And election are about choices, after all.