The leader of America's most prominent communist party credits Vermont Sen. Bernie Sanders with helping usher socialism into the political mainstream, but says it's essential to back Hillary Clinton if she defeats Sanders in the Democratic presidential primary.

John Bachtell, national chairman of the Communist Party USA, says he cast a ballot for Sanders in the Illinois primary in March, but that the self-styled democratic socialist's loyal backers should temper their criticism of Clinton as a warmongering Wall Street puppet.

"The most important thing is keeping our eye on this extreme right-wing danger and really hoping that all political organizations and democratic forces will unite together to try to defeat that," he says.

"Whoever emerges from the primary fight, there will be a very broad coalition to try to get them elected," he says. "We support independence from the Democratic Party and work with forces laying the groundwork for a third party, but it's not realistic in this election."

The nearly century-old Communist Party USA hasn't run a presidential candidate since 1984 and softened its ideology following the collapse of the Soviet Union. It does not advocate the violent overthrow of the government, but rather socialism through the ballot box.

Bachtell, who lives in Chicago, says the party's 5,000 or so members and Sanders are similar in ideology.

"A lot of what he says we've been advocating for a long time – redistribution of wealth, public universal health care, free college tuition," he says. "The bulk of our membership is backing and supporting and voting for Sanders."

Bachtell says "there may be some differences here and there" and that "we probably go way beyond Sanders in the long term in curbing the power of large corporations and banks and expanding the public sector to incorporate a lot of what these companies do."

Many supporters of Sanders have said they aren't inclined to vote for Clinton if she wins the nomination, including actress Susan Sarandon, who said in March she's not sure she would support the former secretary of state and that "some people feel that Donald Trump will bring the revolution immediately, if he gets in then things will really, you know, explode."

Bachtell says he doesn't adhere to the revolutionary strategy of "heightening the contradictions" of capitalism to hasten the arrival of socialism and sees the Green Party, while close in ideology, as a potential spoiler that would help Republicans win elections.

"We don't want to go down that path because there's no telling where it might go," he says. "This idea of making it worse to make it better is a really dangerous proposition, and we've seen this during other periods of history, where the extreme right or fascist-like forces gain ascendancy. There's no guarantee about anything as democratic rights are annihilated or weakened."

He points to Wisconsin, where he says legislation championed by Republican Gov. Scott Walker to combat public sector unions "set back the movement in that state many, many years," and to voter ID laws in states around the country.

The chairman says he fears a GOP-led Congress and President Trump could pass national union-weakening legislation, and that "you can't ask Muslims, who face banning, and undocumented workers facing deportation to wait around a few years for a revolution."

Bachtell says he doesn't believe Trump is a fascist "in the sense of Hitler."

"I do think he's an extreme right-wing demagogue," he says. "It's not only him, it's the forces he's encouraging and some of these are very dangerous forces."

Trump has won enough delegates to win the GOP nomination. And while some party members have sought a conservative independent candidacy, the push has thus far fizzled, though two former Republican governors are on the Libertarian Party's ticket.

Sanders, meanwhile, has refused to back out of the Democratic race, even though Clinton appears on track to capture enough delegates for victory.

Though the word "socialist" has been an insult for decades in American politics, a YouGov survey found earlier this year that more respondents under age 30 had a favorable opinion of socialism than of capitalism. Sanders' campaign has managed to win a significant number of states in the Democratic primary.

"The fact that he's an avowed socialist is a very important thing, and placing a discussion of socialism before the American people and seeing their response to it will have an important effect on politics going forward," Bachtell says, adding he believes Clinton would feel obligated to reward left-wing backers if she wins – even peace groups, despite her reputation for supporting military intervention abroad.

Spokespeople for Clinton, Trump and Sanders did not immediately respond to requests for comment.

Bachtell says many of his fellow Communist Party USA members won't be able to plug their noses and vote for Clinton. But he says they should.