Although labor leaders, local union activists and national progressive politicians uniformly support an Amazon union in Alabama, that feeling does not reflect the mood inside the warehouse itself. With less than a month to go in the union vote, the 5,800-worker warehouse is split among supporters of the union, strong dissenters and an apathetic center that is growing sick of the national attention.

Outside the plant — where some workers clock 12-hour shifts — union activists and journalists are likely to experience a string of exasperated rejections when asking to speak with employees. Some workers wear “Vote No” pins, while others talk of anti-union literature in the common areas and bathrooms. And on social media, employees post about longing for March 29, when the election will conclude.

Amazon has aggressively countered the unionization effort, highlighting the company’s benefit package and its $15 minimum wage, as well as the job growth it has prompted in an economically stagnant area of the South.

Last week, in a media round table of anti-union warehouse workers hosted by Amazon, some said that Mr. Biden’s message had been unnecessary, and that they did not feel intimidated by the company. A spokeswoman for Amazon declined to directly comment on the president’s remarks.

“I know the president weighed in,” said J.C. Thompson, a process assistant at the warehouse. “And I can’t imagine the pressure our leadership is feeling because there’s a few people — a minority — who are disgruntled.”

Carla Johnson, an employee in the warehouse, said she was voting not to unionize.

“I can speak for myself,” she said. “I don’t need someone from the outside coming in and saying this or that.”

The range of opinions hinted at why Mr. Biden’s message was so calibrated — supporting the workers’ right to a fair election but not supporting the union itself. And some observers, including employees at the Amazon warehouse, believe the president’s words will have little bearing on the outcome of the union vote.