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/ Source: TODAY
By Eun Kyung Kim

Eric Trump, the son of the Republican presidential nominee, believes Sen. Ted Cruz "lost a lot of political credibility" when he failed to endorse Donald Trump during his RNC speech.

“I think the audience spoke for themselves,” Eric Trump said about the crowd booing Cruz.

“Don't come out on stage if you don't want to endorse. Or don’t come out on stage if you don’t want to be supportive," Trump told NBC's Peter Alexander.

Trump said he wasn’t sure if the speech was “political suicide” as some have called it, but said Cruz certainly didn’t help his career.

RELATED: Ted Cruz 'made a mistake' at RNC, Trump campaign chief Paul Manafort says

“Listen, I always heard he didn’t have that many friends in Washington, D.C. He certainly didn’t have that many friends in this room last night,” he said.

Trump wouldn’t reveal what his dad would say in his speech Thursday night but said it would take a serious tone.

“He’s not doing this for fun. This is not a joke. He’s put his life aside to run for the most powerful office in the world,” he said.