A formal split in Britain’s Labour Party has become more likely after its executive committee decided on Wednesday that Jeremy Corbyn would automatically stand for the leadership, despite lacking support from lawmakers, and Owen Smith launched a leadership bid of his own.

The parliamentarian from Wales, who resigned from Corbyn’s shadow cabinet last month along with dozens of other frontbenchers, will need the support of 51 of his colleagues to be eligible.

Angela Eagle, a lawmaker from the soft left of the party, already appears to have the support needed to challenge Corbyn.

The risk is that Eagle and Smith will split the anti-Corbyn vote when unseating Corbyn is a tall order to begin with.

Union support

The leftist, who unexpectedly won the leadership last year after spending three decades on the backbenches, can count on the support of left-wing activists and trade unions.

The latter have stuck with him despite a YouGov poll (PDF) showing ordinary union members no longer approve of Corbyn’s leadership.

Len McCluskey, the leader of Unite, Britain’s largest trade union, is an outspoken Corbyn supporter who has warned that his opponents in the parliamentary party could split the entire Labour movement if they don’t surrender.

But only a third of his members still have confidence in Corbyn.

Unelectable

Most probably agree with lawmakers that Corbyn’s antiquated economic views and pacifist foreign policy will make Labour wholly unelectable in the next election.

Former Labour Party leaders, including Neil Kinnock and Tony Blair, have said as much. Polls predict Labour would win even fewer seats today than it did in 1983, the year Corbyn was first elected. It got 209 out of 650 seats in the House of Commons that year, under the leadership of the far-left and antinuclear Michael Foot, against 397 for Margaret Thatcher’s Conservatives.

The direction Labour took at the time convinced centrist lawmakers to split off and start the Social Democratic Party. It never managed to rival Labour and ultimately merged with the liberals.

That history explains why today’s center-left lawmakers, despite being in the majority, are reluctant to go their own way.

But Corbyn and his crew, who see this as their last best chance of turning back the block to before Kinnock and Blair rehabilitated Labour, may give them no other choice.