Biden and Sanders poised to debate

By BILL BARROW
Democratic candidates Joe Biden and Bernie Sanders will debate each other on Sunday

The largest labour union in the US is supporting Joe Biden's presidential campaign, with the National Education Association endorsing the former vice president for the Democratic nomination.

The NEA's board of directors chose Biden over his last remaining primary rival Bernie Sanders.

NEA President Lily Eskelsen Garcia, whose union tops three million members, called Biden a "tireless advocate for public education" and "the partner that students and educators need now in the White House".

The union's decision came with Biden on the cusp of stretching out an insurmountable delegate lead over Sanders.

The two candidates meet on Sunday for their first one-on-one debate, two days before four populous states - Arizona, Florida, Illinois and Ohio - hold primaries with a combined 577 delegates up for grabs.

Biden currently leads Sanders by more than 150 delegates with more than half of the national total already awarded, a gap that means Sanders must win 57 per cent of the remaining delegates to wrest the nomination from Biden. There is no precedent for such a comeback.

In the four states that vote on Tuesday, almost 760,000 voters live in households with at least one NEA member, according to the union. NEA officials said the union's PAC would immediate push digital advertising into the four states on Biden's behalf, while also communicating with NEA households.