The university's push has not been all ominous warnings, though. Players were given new iPads when they arrived for the first day of practice after the N.L.R.B. decision, though the university said the iPads were unrelated to the union process and had been in the planning for months. That afternoon, players were taken to a bowling alley for a team party.
"What the university has tried to do is to communicate clearly the university's position to the student-athletes who are going to be voting in the election," the university spokesman Alan Cubbage said. "We have done so following the guidelines and procedures outlined by the National Labor Relations Board. Our position is that we believe that our student-athletes are primarily students. That has not changed."
Indeed, since the day of the N.L.R.B. ruling, Northwestern's message to the players has been consistent and clear: Vote no — for yourselves, for the team and for the university. Northwestern and many others in the college sports world see the creation of a players union as an existential threat to the foundation of the N.C.A.A., and to their athletic programs.
Northwestern's campaign has been a textbook case of how to aggressively battle a union, labor experts say. It adds up to a lot of pressure riding on the broad shoulders of the 76 football players who are eligible to vote Friday by secret ballot. The results may not be known for months while the full N.L.R.B. deliberates on an appeal.
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"These are 18- and 20-year-old kids," said Earl Jones, the father of running back Malin Jones. "This is a really big decision. As a parent, I'm trying to get all the information I can, and I hope my son is, too."
No one has accused the university of breaking any law. Northwestern is allowed to express its opinion on unionization, though it cannot make explicit promises in exchange for votes.
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The formation of a union would mean that the football players were university employees, not students competing in their free time, and that they could be entitled to workers' compensation benefits, unemployment insurance and some portion of the revenue generated by college sports. The College Athletes Players Association is seeking to represent the players.
"Student-athletes don't have a voice; they don't have a seat at the table," Kain Colter, a former Northwestern quarterback who is the leader of the unionization effort, said in January. "The current model resembles a dictatorship, with the N.C.A.A. placing these rules and regulations on these students without their input or without their negotiations."