As with any high-stakes election campaign, the rhetoric between Amazon.com Inc. and its opponents has been testy since workers at the company’s warehouse in Bessemer, Alabama, began voting on whether to join the Retail, Wholesale and Department Store Union.

Matters turned biological on Thursday, when a Democratic congressman revived an old charge that Amazon employees and contract drivers are worked so hard that they have to urinate in bottles. The company quickly denied that, only to see photos of allegedly pee-filled bottles show up online. Missing from the debate was the 2017 video of an Amazon driver defecating in a Sacramento, California, area driveway.

The hard-fought mail-in election began seven weeks ago and ends Monday. As many as 5,800 workers at the facility in Bessemer are eligible to vote to join the union. Both sides have a lot to lose. If the RWDSU prevails, the unionizing drive could spread to other Amazon facilities, some of which are already seeing stirrings of labor activism. A loss for the RWDSU would be a major setback for the U.S. labor movement, which has been in decline for decades.

Here are some of the most poignant barbs:

• “I welcome @SenSanders to Birmingham and appreciate his push for a progressive workplace. I often say we are the Bernie Sanders of employers, but that’s not quite right because we actually deliver a progressive workplace.”

—Dave Clark, Amazon’s logistics chief, responding to news that Senator Bernie Sanders planned to visit Alabama to show common cause with the workers.

• “Paying workers $15/hr doesn’t make you a ‘progressive workplace’ when you union-bust & make workers urinate in water bottles.”

—Democratic Representative Mark Pocan

• “You don’t really believe the peeing in bottles thing, do you? If that were true, nobody would work for us. The truth is that we have over a million incredible employees around the world who are proud of what they do, and have great wages and health care from day one.”

—Amazon responding to Pocan

• “He has members of Congress out here right now, at his plant where he is physically located.”

—Democratic Representative Jamaal Bowman, suggesting that Jeff Bezos, the world’s wealthiest man, was hiding inside the facility to avoid discussing pay and working conditions. Turns out Bezos was in California at the time.

• “Somebody’s lying. Either Amazon is lying or the Postal Service is lying. We tend to believe that Amazon is lying. They’ve told a lot of lies throughout this process.”

—Joshua Brewer, the RWDSU’s lead organizer, on company assurances that it wasn’t spying on a mailbox installed outside the warehouse for ballot collection.