This chart proves that Jeremy Corbyn's awful approval ratings matter - a lot

One of the major arguments critics of Jeremy Corbyn put forward for why he shouldn't be Labour leader is how severely unpopular he is with the general public.

London mayor Sadiq Khan, who officially endorsed Corbyn's leadership rival Owen Smith over the weekend, told the Observer:"Jeremy's personal ratings are the worst of any opposition leader on record and the Labour party is suffering badly as a result."

Corbyn's latest net satisfaction rating was -33%, according to an Ipsos MORI survey. This is the lowest rating any opposition leader has had since Margaret Thatcher's premiership.

Many of Corbyn's most passionate supporters dismiss these figures as unimportant, or unreflective of what they believe is really going on with the public mood.

Even Corbyn himself has implied he doesn't pay much attention to polls. Earlier this month, he suggested polls should be approached with skepticism, and at a rally on Sunday, he said the media needs to "do some maths" and realise how "unusual and important" the size of the crowds which have been turning out to hear him speak are.

The chart below is a wake-up call for anyone who refuses to acknowledge the significance of Corbyn's dismal approval ratings. Produced by University of Southampton politics professor Will Jennings, it illustrates a clear, historical relationship between Labour leader satisfaction ratings and how they performed in general elections.

The chart has been annotated by Business Insider. The original is here.

The chart, which is based on Gallup and Ipsos MORI data, shows how Labour leaders who have enjoyed positive approval ratings have gone on to win larger vote shares in general elections. Blair was massively popular with the public before leading Labour to a landslide majority in 1997.

At the other end of the scale, Michael Foot, who like Corbyn was a radical socialist who was further "left" than the majority of his own MPs, clocked up appalling approval ratings before being crushed by Thatcher in the 1983 election.

This is what the chart looks like when you plot Corbyn's recent -33% rating. Assuming the current Labour leader isn't a remarkable exception from the historical trend, he is currently expected to win somewhere around 30% of the vote in 2020.

This reflects the findings of extensive research performed by Electoral Calculus earlier this month, which projected Labour would win 28.9% of votes in the next election. This would mean another majority victory for the Conservatives.

The evidence is there for all to see. Corbyn is currently leading Labour to defeat.