Unison said 95% of members, which include administrative and nursing staff, had already voted in favour of taking strike action and 98% voted in favour of industrial action short of strike action, in a ballot last month.
In California, where his petition drive fell well short, his campaign is considering new ways to try to get on the ballot -- keeping the information close to the vest lest Democrats try to thwart him.
Unite said it was beginning the legal process to ballot its 450 paramedics and other ambulance staff members for strike action or industrial action short of a strike.