It's been a week since the 'Southbank Seven' took the bold step of leaving the Labour Party and forming The Independent Group. Although the departing MPs gave broadly topical reasons for their departure - namely, Brexit and anti-Semitism - a split has been a long time coming. Since Jeremy Corbyn was first elected leader in September 2015, those opposed to his radical socialist agenda have toyed with forming a new political Party. For many in Labour, it's a surprise they've held together for so long.
Politicians are often accused of failing to learn from lessons of history, and the fate of the SDP (formed by disaffected centrist Labour MPs in 1981) had, until now, deterred today's moderates from jumping ship. Allied with the Liberal Party, the SDP took over 25% of the vote at the 1983 general election but, thanks to the first-past-the-post system, secured just 23 seats. That a new splinter party would be similarly hindered by the electoral system has become an established fact.
For those loyal to Labour, the real lesson of the SDP isn't the perils of FPTP but that a divided left keeps the Conservatives in power. At the '83 election, Margaret Thatcher's Tories surged to almost 400 seats whilst Labour fell back to barely over 200. The party wouldn't win an election for another 14 years.
It's far from certain that the SDP were to blame for Labour's electoral failings during the Thatcher era (they took votes from the Tories too) but today's Labour MP's and supporters have been repeating this line in the hope of preventing further defections. If the Independent Group takes votes away from Labour, it stands to reason that the Tories will benefit.
Although we're still in the very early days of the Independent Group (they're not even a proper political party yet), polls suggest there may be some weight to that argument.
In the last week, five national polls have featured the Independent Group (TIG) or "a new centrist party" with their vote share ranging from 5% to 14%. Comparing these results to the last five polls before the 'split' seems to confirm Labour's worst nightmare.
Prior to the split, Jeremy Corbyn's party was polling at around 36%. Though they trailed the Tories the average gap was only around 3%, within the margin of error. In polls after the split, that gap has risen to almost 8%, driven by a decline in Labour's vote share. The Conservatives have seen small a decline too but, according to the available data, TIG have cost Labour around five times as many votes as they have the Tories.
To reiterate, it's only been a week since the Independent Group formed and there is very little data to work with; one of the polls considered here was even taken before the County Hall press conference. However, recent experience shows that polling trends shape narratives and influences political decisions. Indeed, many pundits have interpreted Jeremy Corbyn's recent decision to back a second referendum as an attempt to stem any further losses to TIG, both MPs and voters.
The Independent Group have boldly ignored the first lesson of the SDP: that first-past-the-post leaves no room for new parties. Although we won't know for sure until the next election, there's no reason to believe that TIG won't suffer the same fate as their predecessors in the 1980s.
According to the polls, the second lesson of the SDP (that a Labour split keeps the Tories in power) is, for now, holding true.