A Bloomberg Business Week profiles Sean O'Brien as part of a younger breed of labor leaders determined to stake out a more confrontational position with employers. 

The 1.4 million-member union is choosing a new president. The leading contender, Sean O’Brien, can’t wait to slug it out with the shipping giant—and then Amazon.

On an October afternoon sultry enough that it has locals complaining, Sean O’Brien takes up his position outside the employee entrance at a UPS processing facility in Palatine, Ill. A former high school linebacker with a shaved head, O’Brien has still a gridiron hero’s physique, and he looks like someone who won’t be moved without a scuffle. That’s probably not a bad impression to make on the brown-uniformed UPS drivers and warehouse workers hustling in and out of the plant as shifts change.

O’Brien, 49, is running for general president of the International Brotherhood of Teamsters, which represents these UPS employees, and he has a message for them. The workers on their way in get the abbreviated version: Your ballot will soon be arriving in the mail; don’t throw it away. He implores them to vote for his slate of candidates.

Click here to read more at Bloomberg Business Week.