Socialism is on the rise, as Sen. Bernie Sanders and Rep. Alexandria Ocasio-Cortez carry the torch in Congress and polls show young people and Democrats warming to the ideology.

Underlying that trend, some critics say, is a higher education system that has pushed these ideas for decades while stifling internal dissent.

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A 2018 report from the National Association of Scholars found that among top-tier liberal arts colleges, 39 percent had zero registered Republican professors in the entire college.

“The academy is, in some sub-sectors, not very healthy right now,” Stephen Hicks, a philosophy professor at Rockford University, told Fox News.

Research in the humanities and social science fields, he said, has the biggest problems.

“For the last 20 years it's mostly been driven by ideological bias,” Hicks said.

A study from last year in The American Sociologist surveyed 479 sociology professors and found that 21 percent consider themselves "radical" while a mere 2 percent consider themselves "conservative."

The findings are in line with past surveys. A 2004 poll found that among sociology professors, 25 percent self-identified as "Marxist,” 49 percent identified as Democrats, and 5 percent as Republicans. It’s not just sociology – in social sciences broadly, more professors identified as Marxist than as conservative.

The lopsidedness of the social sciences impacts students on campuses.

On RateMyProfessors.com, where students evaluate professors, hundreds of reviews say things such as “you basically have to pretend to be a Marxist in order to get an A” and “as long as you show Marxist ideology in your papers you will pass.”

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The tilt may be having real-world effects – students tend to move left in college, and are also more likely to move left when they major in fields with the most politically lopsided faculty.

A 2012 survey in the Journal of Higher Education followed thousands of college students from freshman to senior year, and found that the proportion of liberal arts students identifying as “liberal” or “far left” rose from 45 percent to 52.5 percent as they went through college.

Majoring in the humanities or social sciences was one of the biggest factors – doing so increased the odds of a student shifting left by about 50 percent. On the flip side, majoring in science or business reduced the odds of shifting to the left. So did being involved in a fraternity or sorority.

For those who do shift left, they’re generally being taught not just traditional socialism, but also a newer “postmodern” variant. The newer ideas focus on the relative “privilege” of different race/gender/sexual identity groups.

It was professors with that new focus who popularized concepts like "check your privilege," "microaggressions" and "intersectionality."

Promotors of such ideas say they are fighting against oppressive groups and trying to achieve “social justice.”

A typical college guide explaining the importance of such concepts reads: “Recognizing and understanding privilege is an important step to understanding individual and societal advantages and disadvantages.”

Such ideas only recently entered mainstream discussions, but have often rapidly found their way into laws, corporate policies and politicians’ statements all across the western world.

A handful of embattled academics warn that such ideas are tearing society apart by separating people based on group identities.

“We've been publicly funding extremely radical postmodern leftist thinkers who are hell-bent on demolishing the fundamental structure of Western civilization,” University of Toronto psychology professor Jordan Peterson said in an interview with the Epoch Times.

Peterson argues that identity politics evolved from the general ethos of Marxism, saying that when Marxist economics became unpopular in the 20th Century after failing in the Soviet Union, many leftist professors “played a sleight of hand” and shifted their focus away from a perceived battle between capitalists and workers – and toward a battle between “oppressor” and “oppressed” identity groups instead.

Professor Stephen Hicks, who wrote a book called “Explaining Postmodernism” on the connection between old-line Marxism and the newer “postmodern” leftism, says there are two major links in thought.

One is that both Marxism and the newer leftist ideas treat people as groups rather than as individuals.

“The other thing they have in common is the adversarial use of terms,” Hicks said. “The ideas of ‘microaggressions’ and group identity are being used as clubs, as weapons against people. They say, you have a certain group identity, and ... we want you to feel guilty and ashamed if you're not in the right group.”

Hicks noted that the newer ideas are not directly Marxist, but “coming out of, broadly, leftism. And since Marxism has been the most significant form of leftism for the last two centuries, it has a lot of Marxist roots in it.”

Fox News asked 10 professors who have supported Marxism or postmodern theories to weigh in on these issues, but none did.

Despite the many shared approaches, experts note that old-school Marxist and “postmodern” leftists often fight each other.

Hellen Pluckrose, editor of the academic Aero magazine, told Fox News that old-line Marxists often see identity-focused leftists as “economically-privileged elite academics abandoning the working class.”

The new leftist approaches have even given headaches to old-school socialists in national politics. Black Lives Matter protesters stormed the stage of a Bernie Sanders event in 2015, forcing him to cancel his speech. In 2017, Sanders also canceled a speech at a “Women’s Convention” after activists blasted allowing a white man to speak there.

Similar battles rage on the left within university fields where conservatives are almost non-existent – but both groups agree on the importance of socialist ideas. The professors who remain open to conservative ideas in such fields say the need for pushback against the new leftists is critical.

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“People are afraid to speak up and oppose the radicals, but you've got a choice -- you can wait around until things get worse,” Peterson has said. “Or you can stand up now and speak.”

Maxim Lott is Executive Producer of Stossel TV and creator of ElectionBettingOdds.com. He can be reached on Twitter at @MaximLott.