Conversations with employees, corporate representatives, union organizers and labor experts Wednesday shed some light on why Senate food service workers decisively rejected a union organizing effort this week.

Workers voted 72-37 on Tuesday against joining the Mid-Atlantic Regional Joint Board of Workers United, a local affiliated with the Service Employees International Union.

Multiple sources suggested the vote might have been a referendum less on representation itself than on the SEIU.

While Senate food service has been privatized only since 2008, House food service workers have been under private contract since 1986 and unionized for almost as long under Unite Here Local 23, an AFL-CIO-affiliated union. Some House food service workers said they lobbied their Senate counterparts to reject the SEIU and consider Unite Here instead.

That might not be possible, though, under a deal struck between the two unions.

After a prolonged jurisdictional feud between Unite Here and SEIU, the unions reached a 2010 truce designating where each can organize.

Today, Unite Here can represent food service workers at stadiums, convention centers, private companies and airports, according to a Washington Post article published at the time of the settlement. Food service workers in government buildings now fall in the SEIU’s domain. The House workers’ affiliation with Unite Here is grandfathered into the deal.

“I can only surmise that employees voted not to be represented by SEIU,” said Emilio Abate, a lead organizer for Unite Here who works with the House food service workers.

Additionally, Senate food service employees risked losing certain benefits — now guaranteed under their contracts with Restaurant Associates, the private firm that manages food services in the House, Senate and Capitol Visitor Center — during any collective bargaining period that would have followed certification of the union.

“I like what I have now,” one said.

Union officials see a more nefarious reason behind their defeat — they argue that Restaurant Associates used improper tactics to sway workers’ votes.

The National Labor Relations Act prohibits employers from conducting “surveillance” of employees to ensure they aren’t engaging in pro-union activities. The Regional Joint Board alleges that Restaurant Associates conducted surveillance that scared workers away from supporting the union. Union officials said they are considering filing formal charges with the National Labor Relations Board.

The union was already making those allegations before the vote, which might be an indication that it expected to lose.

In any case, Restaurant Associates spokeswoman Gina Zimmer waved away the charges before voting took place.

We “respect our employees’ right to make an informed decision as to whether to be represented by a union … [and] all information provided in response to the employees’ questions has been factual and in accord with law,” she said.