"Donald's campaign, his entire campaign is built on a lie," Cruz told the CNN.
"Every time Donald gets scared, he begins lashing out. He begins attacking. He begins insulting. He begins yelling. Often, he begins cursing. I'm impressed Donald managed not to curse in that particular riff. But give him a minute, that will change," the 45-year-old Cruz said.
Cruz was responding to a question about the 69-year-old Trump's stump speech in which he is described as "liar Ted".
Cruz said he understands the people who are supporting Trump.
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"They are frustrated with Washington, with politicians in both parties that have been lying to us, that make promises and they go to Washington and they do the exact opposite of what they said," he said.
"But if you are fed up with Washington, with the corruption of Washington, then it doesn't make any sense to support Donald Trump who has been enmeshed in the corruption of Washington," he added.
"Trump has supported liberal Democratic politicians for 40 years from Jimmy Carter to John Kerry to Joe Biden to Chuck Schumer to Harry Reid to Hillary Clinton as a presidential campaign.
Trump has enriched himself using government power.
"And in every instance, Donald believes government is the solution, whether it was supporting the Wall Street bailout, which he did, he supported Obama's bailout, supporting the Obama stimulus plan, or using eminent domain to take the homes of little old ladies, or to try to do so, in order to build a parking lot for his casinos," he said.
"Hillary wins. Donald may be the only candidate on the face of the planet that Hillary Clinton can beat in a general election. The stakes are too high. If you are fed up with illegal immigration, Donald Trump funded the "gang of eight" that pushed the massive amnesty plan. I led the opposition to it," he said.