The Amazon Labor Union has built momentum leading up to an election starting Oct. 12 at an 800-person warehouse near Albany, N.Y.

The New York Times reports that a federal labor official recently endorsed the union’s election victory at a Staten Island warehouse in April, which Amazon has challenged, while workers’ frustrations over pay and safety have created an opportunity to add supporters and to pressure the company to bargain.

But the union faces questions about whether it can translate such opportunities into lasting gains. For months after its victory at the 8,000-person warehouse on Staten Island, the union appeared to be out of its depths. It nearly buckled under a crush of international media attention and lost a vote at a second Staten Island warehouse in May.

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The election near Albany, to be spread out over four days between Oct. 12 and Oct. 17 in Castleton-on-Hudson, could help determine whether the earlier problems were natural growing pains or a sign of deeper dysfunction.

Amazon has cast doubt on the Amazon Labor Union’s experience and says it doesn’t believe that the union represents workers’ views. The company said it was investing $1 billion over the next year to permanently raise hourly pay.