Republican primary front-runner Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE on Sunday took credit for the success of surging Democratic primary candidate Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE.

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Trump said his attacks on Democratic front-runner Hillary Clinton have allowed Sanders to leapfrog her in some polls.

“Look, I was the best thing that ever happened to Bernie Sanders, because my attack on Hillary — all of a sudden she went down, and Sanders got all the credit for it, right?” Trump said at a rally in Muscatine, Iowa.

“And then they start saying, ‘Bernie Sanders is surging, an amazing thing happened.’ I did it. I’m saying I did that,” he added.

“This guy Bernie Sanders — give me a break. How does he figure this whole thing? But he got all the credit — it’s unbelievable.”

The billionaire businessman said he is refraining from attacking Sanders because he doesn’t want to bolster Clinton’s campaign.

“I mean, here’s a guy, he’s a — well, they say socialist, but some people would say he’s a communist, OK?” he said.

“But I shouldn’t hit him too hard, though, because if I hit him hard, he’ll go down and then it’ll be more of a fight with Hillary, and maybe we won’t have to fight for a while,” he added. “So I’ll say, ‘Isn’t he a wonderful guy?’”

Trump continued that he could launch devastating attacks against Sanders at any moment, but said he was hesitant because it would be “too easy."

“So now maybe I should hit — oh, I could hit him,” he said. “I have stuff in my mind. I could sit him so hard he would drop. He would drop. No, he’s — he’s — no, he’s too easy. He’s too easy. He’s really too easy.”

During the rally, two — including one man wearing a red turban — draped a sign over an auditorium balcony that read, “Stop Hate.”

WATCH: Protester in turban removed from Trump rally after unfurling "Stop Hate" banner https://t.co/RKgXupNUsP https://t.co/SSVKOKbQyc — ABC News Politics (@ABCPolitics) January 24, 2016

“He wasn’t wearing one of those hats, was he?” Trump asked the crowd after the men were escorted out of the venue.

“Was he wearing one of those? And he never will, and he never will, and he never will, but that’s OK, because we have to do something folks, because it’s not working,” he added.

It is unclear whether Trump was referring to one of his signature “Make American Great Again” hats or to the man’s head garb.