Presidential candidates Donald Trump and Sen. Ted Cruz (R-Texas) engaged in a bizarre back-and-forth on Twitter over the weekend, with at least one admitting to being a "maniac."

The exchange was set off after Cruz questioned Trump's "judgment" to be president at a private fundraiser last week, then rolled back slightly by saying voters would choose the candidate with better judgment. Unlike some of his contenders, Cruz has largely avoided public spats or name-calling with the businessman.

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Trump later called Cruz out for taking jabs behind closed doors, saying in a CNN interview on Sunday that he had "far better judgment" than the senator, adding in a separate Fox News interview that Cruz's "maniac" temperament wasn't White House material. The candidate also took to Twitter Sunday night to press Cruz on his comments.

Addressing Trump's comments just over 10 minutes later, Cruz tweeted the following.

The exchange came as polling shows Cruz rising in popularity among likely Republican Iowa voters, where Trump leads. On Monday, the Des Moines Register reported that Cruz had taken the lead over Trump there. Some speculated that the lead could make Cruz a target for Trump at Tuesday night's GOP debate. Judging from his needling in the past, that's not unlikely.

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Cruz, for his part, didn't take the bait last week.

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