Nearly 60 percent of Democratic insiders in the first four nominating states say the businessman — who has mostly avoided tapping his vast personal fortune to fund his campaign — would be the easiest of the leading GOP candidates to defeat in the general election.

Roughly two out of three picked Rubio from a list of five leading GOP contenders — including Trump, Ben Carson, Ted Cruz and Jeb Bush — as the most formidable GOP hopeful due to his biography and political skill.

“We all want to believe [Trump’s] support base cannot grow much more,” said a Nevada Democrat. “[Rubio] does a superb job of using his story in his campaign; of all Republicans, he has the best [only] chance of reaching Hispanic voters; his youth and charisma are contrast to [Hillary] Clinton.”

“Rubio excites audiences that hear him — he’s an optimistic face on regressive policies — which makes him very dangerous,” added a South Carolina Democrat, who like all the insiders, completed the survey anonymously.