Sanders is not as far left as Corbyn, of course. No elected US politician is as far left as Corbyn, who promises to nationalise the railways and energy companies, scrap university tuition fees, bring back rent controls, raise taxes and introduce a national maximum wage to cap the wages of bankers and other high earners, impose an arms embargo on Israel, and get rid of Britain's nuclear weapons.
When asked if there were any circumstances under which he would deploy British armed forces abroad, Corbyn replied: "I'm sure there are some but I can't think of them at the moment." He is a republican, although he says that ending the monarchy is "not the fight I'm interested in". He's a vegetarian who does not own a car.
Bernie Sanders, by contrast, lives in the United States, where many people regard "democratic socialism" as akin to devil worship. He favours universal healthcare funded by taxes (supported by all parties in Britain) and publicly funded elections with strict limits on corporate donations (ditto), and he too advocates free higher education and higher taxes on the rich. That's already "socialist" in an American political context.
But he's not planning to nationalise anything, bring in rent controls, end all American military interventions overseas, or ban arms sales to Israel. Whatever his private opinions may be, he is running for the Democratic Party's presidential nomination, and nobody in the Democratic Party has advocated anything that radical within living memory.
Sanders is as far left within the American political spectrum (which doesn't extend very far in that direction) as Corbyn is within the broader British spectrum. Could he really pull off a Corbyn-style upset and win the Democratic nomination?
It depends on whether Hillary Clinton's current stumbles end in a big fall in her support. It could happen. Last week's opinion polls revealed that she had lost her lead over her two likeliest Republican opponents in next year's presidential election, Jeb Bush or Ben Carson - and even Donald Trump was drawing level with her.
The Democratic National Convention is still 10 months away, but it's already late for anybody other than Vice-President Joe Biden to enter the race with a good chance of winning - and Biden is deeply conflicted about running.
So if Clinton fades, Sanders would have a chance: the odds against him are already a good deal shorter than 200-to-one. Whether he could actually win the presidency is a different question.
British pundits were unanimous in saying that Corbyn has no chance of winning a national election and becoming prime minister. Former Labour leader and prime minister Tony Blair went further: "If Jeremy Corbyn becomes leader it won't be a defeat like 1983 or 2015 at the next election. It will mean rout, possibly annihilation."
But Labour just lost the last election and the next one is five years away. There is still time to change horses if Corbyn isn't working out. Whereas the US election is next year. Could Sanders win it? The professional pundits and pollsters in the United States say no, because he's too far from the mainstream.
Sanders just points to the despair that grips so many middle-class Americans as the rich get ever richer and their own living standards stagnate.
"Don't let anybody tell you that we're radical, that we're outside the mainstream. We are the mainstream." He could be right. It's the same despair with business as usual that has pushed Donald Trump out in front of the Republican nomination race.
And that would be something, wouldn't it? Bernie Sanders vs Donald Trump for the presidency. At last Americans get a real choice.
-Gwynne Dyer is an independent journalist whose articles are published in 45 countries.
