The extraordinary thing about that sentence is that in the context of modern British and European politics it might be shocking, but it is not surprising.Corbyn, who according to opinion polls stands a good chance of being the next British Prime Minister, has a history of associating with fringe left-wing groups whose support for the Palestinian cause often bleeds into anti-Semitism.His rise to the Labour leadership has brought with it views that were on the fringes of politics into the mainstream — and in this, he is part of a pan-European change in politics.Over the past decade, Europe has seen a rise in the success of far-right and far-left political parties.In France, Marine Le Pen's Front National swept aside traditional parties and gained more than a third of the votes cast in the Presidential election.In Germany, the nationalist Alternative for Germany (AfD) gained nearly 10% of the vote in the last election and the first representation in the German parliament, the Bundestag, for extreme-right parties since the fall of Nazi Germany.In Greece, the radical left-wing party Syriza runs the government.A similar pattern can be seen across Europe — a decade-long rise of previously marginal parties to influence and sometimes power. So marked is this rise of populism that Steve Bannon, the controversial alt-right leader, has moved to Europe, declaring it the crucible of the future of politics.What's going on?One simple explanation is that since the crash of 2008 and the recession that followed, a long shadow has been cast over European politics.Voters across Europe see it like this: the banks crashed the global economy and were then bailed out with taxpayers' money, but hardly any bankers went to jail and workers haven't had a meaningful pay increase for a decade. Framed in this way, the revolt against the establishment is utterly understandable — but the consequences are complex. Not only are established parties blamed by voters for perceived complicity in the crisis, they are also found at fault for offering no solutions of substance to the fundamental economic problems.Politics, though, abhors a vacuum, and across Europe, fringe parties of the left and right have moved to center stage by offering populist solutions with growing support.Those fringe parties have brought with them all the baggage of fringe ideologies, among which some of the most prominent are conspiracy theories including one of the oldest and most pernicious — anti-Semitism.Sadly, Corbyn is not alone among the leaders of European political parties in having brought an anti-Semitic strain into the mainstream. What he is, though, is a rare example of someone who has done this within an existing mainstream party.For Americans looking to Europe, this must all seem alien.The same political forces that have driven the rise of extremist parties in Europe are present in the US and they have produced a populist politics on the right and the left. But they have not unleashed anti-Semitism as in Europe.What is the cause of the difference? Partly, it is that the duopoly of the Democrats and the Republicans doesn't only squeeze out third parties, it keeps fringe parties where they should be — on the fringes.Partly, it is that the US moral mission as the world's policeman since the Second World War has meant that its support for Israel has been mostly unwavering.Mainly, it is because of the vigilance of the Jewish community within the US challenging and combating anti-Semitism whenever it surfaced, and their involvement in both mainstream parties.No American politician could do as Corbyn did without destroying their political career. Europeans often feel that their political systems are superior to the US'. In this case, Europe needs to learn urgently from America.