“Look, he took a drink of water in a speech. And it dominated the news for days with one network saying it was a career ender," Cruz said.

Cruz hinted that there could be racial motivations behind the criticism, saying the backlash was fueled by more than Rubio's "promising" political outlook.

"I think the Democrats view Marco RubioMarco RubioWhat Trump's Cabinet picks reveal House passes water bill with Flint aid, drought relief What the 2016 election can tell us about 2018 midterms MORE as a particular threat because of his background, his life story. I think it they believe it is in their interest to inflict as much damage as possible and blow things wildly out of proportion," Cruz said.

Rubio, the child of Cuban American immigrants, has been heralded by many in the GOP as someone who could improve the party's image with Hispanic voters, after they broke overwhelmingly for President Obama in the 2012 election. A Time magazine cover story earlier this month depicted Rubio as "The Republican Savior" and called him the "great Hispanic hope of the Republican Party."