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- Biden's union allies are questioning his candidacy, according to The Washington Post.
- The publication said union leaders want Biden to spell out his plan for beating Trump.
- Biden is coming under increasing pressure to step aside after his disastrous debate against Trump.
Joe Biden this week described himself as the most pro-union president in US history.
"I think of you as my domestic NATO — not a joke," the president said during a speech on Wednesday to the executive council of the AFL-CIO, America's largest federation of trade unions.
Biden regularly plays up his support from unions, and he may just be counting on it for his survival.
But that support could be about to break.