BERNIE SANDERS is on a roll. His political rallies attract bigger crowds than those of any other contender for the presidency. More than 15,000 showed up to hear him speak in Seattle, 27,000 in Los Angeles and 28,000 in Portland. His audience at the Iowa state fair was bigger than The Donald’s. One recent poll put him in the lead in New Hampshire, the site of the first primary contest. When Mr Sanders turned up, around half an hour late, at a historic theatre in posh Lincoln Park on Chicago’s North Side, he was warmly welcomed by a largely white, mostly young audience of more than 800 who had forked out between $50 and $1,000 to hear him speak. He was introduced by four stalwarts of progressive politics in Chicago: Chuy Garcia, the Cook County commissioner, who had challenged Rahm Emanuel in the mayoral election earlier this year; Susan Sadlowski Garza, an alderwoman and vocal member of the Chicago Teachers Union; Carlos Rosa, who was elected alderman at the tender age of 26, and Robert Peters, an African-American from the National People’s Alliance. They all praised Mr Sanders as the one person who is speaking “truth to power” and called for the audience “to feel the Bern”.

As the 73-year-old senator from Vermont, who describes himself as a Democratic socialist, took the stage his voice sounded raspy, as if it wasn’t going to last long. Yet as he outlined his progressive credo point-by-point, his voice grew stronger. By the end he was almost shouting “enough is enough” as he called for a “political revolution” to fix America’s broken political, economic and social system.

Mr Sanders’s programme is a frustrating mix of sensible progressive proposals and contradictory utopian ideas. He rightly deplores the role of money in politics, calling the campaign-finance system “corrupt” because it allows billionaires to buy huge political influence. He wants to revoke the ruling in Citizens United v Federal Election Commission by the Supreme Court in 2010, which, he says, opened the floodgates of unlimited political donations by corporations and fat cats and created an oligarchy. “We allowed rich people to buy the US government,” he railed, emphasising that he doesn’t have a super PAC, the vehicle through which the rich channel huge political donations. So far Mr Sanders has raised $15.2m for his campaign from 350,000 individual supporters (more than any other contender); the average donation is $31.

Mr Sanders is appalled by America’s increasing inequality, where one-tenth of the top 1% own as much as the 90% at the bottom. He deplores the plight of the working poor and wants to introduce a mandatory nation-wide $15 minimum wage. He is in favour of paid maternity leave, paid sick leave and at least two weeks of paid holidays. He wants to end institutional racism and reform the broken criminal-justice system by rethinking the “war on drugs” and mandatory minimum sentencing. And he says America must find a path to citizenship for the country’s 11m undocumented immigrants, who are often exploited and live in fear of being deported to their home countries.

So far, so reasonable, for those on the left of the political spectrum. Yet when it came to some of his reform ideas and, most importantly, how to pay for them, Mr Sanders changed from what seems a practical Social Democratic course to an unrealistic, even retrograde line. He wants “Medicare for all”, free health care for everyone as well as free public universities and help for those saddled with tens of thousands in student debt. And he plans on spending $1 trillion on repairing and expanding America’s crumbling roads, railways, bridges and other infrastructure. How to pay for all that? A tax on Wall Street speculation will cover it, he says, arguing that America’s middle class bailed out Wall Street during the financial crisis, so it’s now Wall Street’s turn to pay for the middle class. “The billionaires must pay their fair share,” he says, vowing to stop the rich from hiding their billions in the Cayman islands and other offshore tax havens.

Mr Sanders’s most dangerous proposal may be linked to his promise to stop the outsourcing of jobs. He says that he opposed NAFTA and is now fiercely opposed to TTIP, the Transatlantic Trade and Investment Partnership, an ambitious planned trade deal between America and the European Union, as well as TPP, the Trans-Pacific Partnership, a 12-country trade pact. With such protectionist policies, Mr Sanders is oddly close to the man in public life he would like least to be associated with: Donald Trump.