Chicago Mayor Rahm Emanuel’s appointees at the Chicago Transit Authority are accused of illegally blocking employees from sharing literature related to the city’s mayoral race, in a lawsuit filed in federal court Tuesday by the transit workers' union.

The CTA posted memos in bus garages and rail terminals telling employees not to engage in political activity on “taxpayer-funded property,” including in break rooms, according to the Amalgamated Transit Union, which represents 10,000 Chicago bus and subway employees. The union has endorsed Emanuel’s challenger, Jesus “Chuy” Garcia. The CTA’s general counsel also warned the union that employees could be fined if they violate the policy, according to letters provided to International Business Times.

A copy of the memo provided to IBTimes is dated March 12 -- more than two weeks after a strong showing from Garcia in the first round of Chicago's mayoral election prevented incumbent Emanuel from getting the necessary 50 percent of the vote to avoid an April 7 runoff. The union has distributed fliers that read "Transit for Chuy."

In the past, the Chicago Transit Authority has allowed employees to distribute political material in break rooms on non-working time, according to the lawsuit. The union called the policy change “an unprecedented act of political repression.” 

“I’ve seen brutal attacks on working people in the last few years, but this is a new level of repulsive behavior,” ATU President Larry Hanley said in a statement. “When the leader of the Democratic Party in one of America’s largest cities threatens public workers and suspends their First Amendment rights, it’s time for the national Democratic Party to step in. Today, I’m calling on the entire Democratic Party to repudiate Rahm Emanuel.”

Hanley points out that Emanuel held a press conference Friday in the work area of a city bus garage, where he announced the expansion of a city internship program. Rep. Bobby Rush, D-Ill., who has endorsed the mayor’s re-election, was in attendance and wearing an Emanuel campaign button at the time, according to the lawsuit.

“If it’s unethical for a bus driver to talk to a bus driver about the election, why is ethical for Rahm Emanuel to come into a garage and hold a political event?” Hanley says. “This smells of unfair advantage and bullying.”

Without knowledge of the case specifics, American Civil Liberties Union staff attorney Lee Rowland said courts generally uphold strong political speech protections for public employees, especially when attempts to muzzle it can be perceived as efforts to engage in political patronage. 

In letters sent to the union, which were provided to IBTimes, the CTA argues that state law does not allow political campaign materials -- save those for union elections -- in public workplaces.

The CTA did not immediately respond to a request for comment.

A poll released Tuesday showed Emanuel leading Garcia by 58 to 30 percent.