"I think he has a chance. He's sending a message to the middle class," Icahn said on CNBC's "Fast Money: Halftime Report." "I don't know why you wouldn't vote for someone with that message."

Icahn contended that electing the controversial billionaire businessman would be a "no-brainer" for American voters. He echoed the anti-establishment sentiment that took Trump to the top of the polling for the Republican presidential nomination this summer.

Activist investor Carl Icahn doubled down on his support for his friend and presidential candidate Donald Trump on Wednesday.

Trump currently leads the GOP field for the 2016 nomination in most national polls, seeing a meteoric rise in recent months while portraying himself as an outsider from politics and defender of the middle class. He has received backlash for comments on immigration and women's issues as well as a lack of specific policy proposals.

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Icahn defended Trump, saying he is a "very open-minded guy" who listens to input. He also touted Trump's appeal to conservative voters, stressing that he supports limited government more than other Republican candidates.

Icahn added that he believes Trump has the background to take on business interests and the pay gap between chief executives and their workers.

The billionaire investor has repeatedly said he would decline Trump's offer to become Treasury secretary should he win the White House. However, Icahn noted that he would "certainly be there to advise him if he wanted it."

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