In just over three weeks' time, Jeremy Corbyn will be declared the new Labour leader. This is the assumption that the PLP and all rival parties are operating under. The Tories are divided between those intoxicated by the prospect of remaining in office until at least 2030 (they predict) and those who fear that a Corbyn-led Labour Party will drag them leftwards by redefining the centre of British politics. Thoughtful types also worry that a weak, divided opposition will lead to less scrutiny and worse government.

But what of the Lib Dems? Some have predicted that Corbyn's election could offer the vanquished party an early means of revival. "It would be like Lazarus, they would rise from the dead, if Jeremy Corbyn was to become leader, rejuvenate them when they're actually down and out," Jack Straw recently said. This prediction is premised on the belief that the Lib Dems would provide a home for centrist voters fleeing a radically left-wing Labour Party, as the SDP did in 1983. At that election, the third party came close to supplanting Michael Foot's opposition on vote share, winning 25.4 per cent to Labour's 27.6 per cent. If there is a voter revolt against the Conservatives, the Lib Dems may benefit in those seats, most notably in the south-west, where they remain the opposition. But the potential for gains is more limited than Straw suggests. There are only 62 seats in which they are in second place and in just 16 of those do they lie within 10 points of the incumbent. The arithmetic does not suggest a Lazarus-style recovery.

While a Corbyn leadership may help new leader Tim Farron to attract moderate voters from Labour, it will make it harder for him to win over left-leaning ones. His early policy stances, such as opposing the welfare reform bill and military action in Syria, showed how he hoped to fish in this pool. The election of Andy Burnham, Yvette Cooper or Liz Kendall would allow him to continue to do so (though the Corbynites could drag them leftwards). But unless Farron proposes an insurrectionary assault on Buckingham Palace, he will struggle to find any space to Corbyn's left.

Whoever wins the Labour leadership, the biggest challenge for the Lib Dems remains the simple struggle for relevancy. Unlike in previous decades, when the UK was a three-party system, the Greens and Ukip provide alternative repositories of protest. A swing away from Labour was once a guarantee of a swing towards the Lib Dems. But no longer.