Oakland, Calif.

For the past 10 months, the SEIU has fought to hold on to 150,000 members in its Union of Healthcare Workers affiliate, or UHW. The challenge comes from a group of former UHW leaders and Stern confidantes. Pushed out by Mr. Stern after a prolonged power struggle, they started a rival outfit, the National Union of Healthcare Workers, or NUHW, in January and immediately moved to build it up by wooing away members from the SEIU's local, UHW.

Now these upstarts charge that the UHW threatened workers with deportation and tampered with secret ballots to narrowly win a pivotal election last summer in Fresno, Calif. The NUHW allegations, contained in a complaint filed last Friday and previously not made public, take the battle to a new level.