CARACAS, Venezuela—President Nicolás Maduro, hoping for an economic miracle to salvage his country, has placed his trust in an obscure Marxist professor from Spain who holds so much sway the president calls him “the Jesus Christ of economics.”

Alfredo Serrano—a 40-year-old economist whose long hair and beard have also elicited the president’s comparison to Jesus—has become the central economic adviser to Mr. Maduro, according to a number of officials in the ruling United Socialist Party and other government consultants. His...