Public service union leader Nadine Flood faces an uphill battle - this time around - in her long-held ambition to become a Labor Senator.
Ms Flood, the National Secretary of the Community and Public Sector Union, is in the running to replace NSW Senator Doug Cameron when the veteran firebrand retires at the next election.
But the CPSU secretary is up against tough opposition with the powerful Australian Manufacturing Workers Union backing its NSW Secretary Tim Ayres, to take the winnable No.2 spot on the state's Labor Senate ticket.
Labor sources confirmed on Monday that Ms Flood was in the running for the upper-house seat, but that the feeling in the party was that she would lack the numbers to prevail.
Ms Flood would not be drawn on Monday on her political ambitions.
"Our members face a sustained attack from the Turnbull Government on their jobs, rights and services, and I'm committed to leading them in those fights," she said.
