DES MOINES, Iowa — Republican presidential candidate Donald Trump has finally unleashed a verbal assault on the one rival he has so far spared.

Trump went after Ted Cruz at a town hall event in Iowa Friday evening, accusing the Texas senator of being beholden to big oil companies because he opposes ethanol subsidies, which are deeply popular in this agricultural state.

“He’s a nice guy. I mean, everything I say he agrees with me, no matter what I say,” Trump began. “But with the ethanol, really, he’s got to come a long way.”

He added: “If Ted Cruz is against ethanol, how does he win in Iowa? Because that’s very anti-Iowa.”

Trump also appeared to take a veiled shot at Cruz’s family background, suggesting Cruz might have trouble appealing to the state’s evangelical voters. “I do like Ted Cruz, but not a lot of evangelicals come out of Cuba,” he said of the country where Cruz’s father, an evangelical preacher, was born.

The attacks came after The New York Times reported that Cruz had questioned Trump’s judgment at a closed-door fundraiser, straining the rare detente between two of the race’s most outspoken candidates.

Trump has gone after his other opponents gleefully and viciously, panning Jeb Bush as low-energy, Ben Carson as “pathological” and Marco Rubio as a lightweight who drinks too much water.

But the billionaire businessman had refrained from attacked Cruz, even as the Texas senator has surged in opinion polls, becoming Trump’s most serious challenger in early-voting Iowa.

Trump previewed his attack lines on Twitter Friday morning.

Cruz “should not make statements behind closed doors to his bosses, he should bring them out into the open — more fun that way!” he wrote. Trump predicted Cruz would “fall like all others. Will be easy!”

In the audio leaked to the Times, Cruz said his approach has been to “bear hug” Trump. But he appeared less than eager to engage on Friday.