Rep. Ro Khanna (D., Calif.) had a warning on Sunday to his fellow Democrats: don't underestimate President Donald Trump in the 2020 election.

Khanna appeared on CNN's "State of the Union," where host Jake Tapper asked left-wing activist Nina Turner if she believed Trump would be the easiest candidate for Democrats to face in 2020.

Trump is suffering from low approval ratings, but he overcame a low favorability rating and almost all major polling predictions in 2016 to defeat Hillary Clinton.

Turner a supporter of Sen. Bernie Sanders (I., Vt.), did not say who she would like to see matched up in the general election, leading Khanna to jump in and say that Trump shouldn't be underestimated.

"We shouldn't underestimate him," Khanna said. "His appeal to communities was, ‘Everyone else has forgotten you and I'm going to bring you back. I'm going to restore that dignity and pride.’"

Khanna then said that Democrats need to reach out to those who feel the Democrats are not working for them anymore.

"We have to give an aspirational economic message to these communities to say you can have opportunity in the 21st century, that we haven't forgotten you, that we want to harness your talent and hard work and we've got work to do as a party," Khanna said.