On Tuesday, CNN anchor Anderson Cooper accused Donald Trump of using the logic of a five-year-old to defend an online insult directed at Texas Sen. Ted Cruz's wife last week.

Cooper asked Trump about a side-by-side photo comparing the attractiveness of Heidi Cruz and Trump's wife, Melania, which appeared on the candidate's Twitter feed — the culmination of an online spat between the top two GOP candidates.

"After saying that you were going to 'spill the beans' about Heidi Cruz, you retweeted an unflattering picture of her next to your wife," Cooper said.

"I thought it was a fine picture of Heidi," the candidate said.

"She's a pretty woman," he added, explaining that he "didn't start it."

Cooper shot back: "Sir, with all due respect, that's the argument of a five-year-old."

Here's the full exchange:

Where did all of this start?

Ahead of the Utah caucuses earlier in March, an anti-Trump super PAC released a meme (above) featuring Melania Trump's photo shoot with GQ magazine. Trump accused Cruz of knowing about the meme before its release, and threatened to "spill the beans" on Heidi Cruz. Some presumed the threat to be a reference to a public battle with depression, during which Heidi was spotted sitting on the side of a highway in Texas.

Instead, the candidate manually retweeted a photo that apparently rendered his earlier threat useless:

At a news conference the following day, Cruz called Trump a "sniveling coward" over the tweet, telling the candidate to "leave Heidi the hell alone."

The exchange was highlighted at Tuesday's CNN town hall, as part of a larger discussion about Trump's confounding political and professional decorum — which often runs off the rails on Twitter.

When Cooper pointed out that it was often the things that Trump retweets that get him in trouble, the two seemed to be in agreement.

"My biggest problem is repeats and retweets," the candidate said.