Jeremy Corbyn and his supporters argue that he is electable because he can attract large crowds to his rallies. For instance, look at these photos showing an event in Merthyr which @JeremyCorbyn4PM tweeted on Friday. Corbyn has been able to attract larger crowds than Owen Smith, and he doesn't even need to offer free ice cream. Over 1,700 people attended Corbyn's campaign launch at the Lowry in Manchester. It's Corbyn's popularity amongst a certain part of the electorate which has caused Labour membership to rise to over half a million.

Unfortunately, recent British political history demonstrates that getting thousands of supporters to attend rallies is not a sign of electability. If anything, it proves the exact opposite.

Amazing scenes from Merthyr right now #jeremy4labour pic.twitter.com/pDWBOofCNe — Jeremy Corbyn for PM (@JeremyCorbyn4PM) August 5, 2016

One disturbing precedent is 1983. In this election, Labour leader Michael Foot decided to promote “the longest suicide note in history” by touring the country and speaking to groups of cheering supporters about nuclear disarmament. The week before leading Labour to a catastrophic defeat, Foot spoke to a crowd of 40,000, which you can see a picture of here. There's more footage of Michael Foot addressing crowds in the 1983 election in this documentary from the 1990s. As the Labour veteran John Golding put it: for every thousand people who were cheering at the rally, there were 122,000 outside saying you're crackers.

One large rally at Sheffield may have cost Labour the 1992 election. The idea was to have an American-style “Convention” to glorify Labour's leader, Neil Kinnock. Over ten thousand attended the rally at Sheffield arena which had a budget of £150,000. You can see footage of the rally here.

Neil Kinnock arrived by helicopter and became overcome by the emotion of the moment. “We're alright” he shouted in an unscripted aside which Kinnock thinks cost him the election. As he said later, “This roar hit me and for a couple of seconds I responded to it; and all of the years in which I'd attempted to build a fairly reserved, starchy persona - in a few seconds they slipped away.”

“We're alright,” was all that the BBC showed of Kinnock's speech. That moment of hubris made Kinnock look more like a leader of the Opposition than a Prime Minister, and is a warning to politicians not to be taken in by the huge enthusiasm of crowds they are addressing. The rally also contrasted unfavourably with John Major's soapbox campaign, which made him look more like a man of the people. Nine days after the Sheffield rally John Major's Conservatives won more votes than any other prime minister in British history.

Our final example is 1968. That year saw mass protests, strikes, sit-ins and demonstrations against the Vietnam War in Europe and America. Looking back at 1968, the Irish academic Fred Halliday wrote that he wished the left-wing movements he supported had shown more political realism. Despite all the protests and rallies, the winners of the elections held in the late 60s and 1970 were Edward Heath, Charles de Gaulle and Richard Nixon. Social Democrat Willy Brandt bucked the trend of voters electing right-wing leaders, but the far-left student movement in West Germany castigated him for entering a coalition and instead retreated to the fringes.

Gaining more members and having mass demonstrations have a place in a political movement but is no sure route to electoral success. Without a strategy to win over voters who don't necessarily agree with you, all the idealism and enthusiasm of those who attend Corbyn's rallies will sadly amount to nothing.