Sen. Ron Johnson and Rep. Trey Gowdy are digging deeper into the leave policies of various federal departments in the wake of recent reports that the U.S. Post Office violated the Hatch Act when their employees took official leave to campaign for Hillary Clinton in 2016.

At issue are small bits of the employee's contracts that are negotiated by unions called "official Leave Without Pay," which allows the employees to do political work while on leave from the agency. Johnson, R-Wis, and Gowdy, R-S.C., are the top two oversight members of Congress in their respective chambers.

However, in July, the USPS Office of Special Counsel determined the USPS engaged in an "institutional bias" toward the candidates endorsed by the union, which were largely Democrats.

The Hatch Act restricts the political campaign activity by federal employees.

Johnson and Gowdy both signed letters sent Monday to 10 different agencies in the federal government, as wide and varied as Veterans Affairs, the Social Security Administration, the Department of Justice, and the Department of Commerce.

The letters seek more information, starting in 2008, on the number of employees who requested official leave without pay and the activities they were engaged in while on leave, and even request some of that information in a state-by-state breakout.

As chairman of the Senate Homeland Security and Government Affairs Committee, Johnson played an important role in unearthing the post office scandal after getting a tip from a constituent.

The Hatch Act has been in the news for other reasons in 2017.

Recently, the Republican Governor's Association charged the director of the Consumer Financial Protection Bureau, Richard Cordray, may have violated the Hatch Act. Cordray is assumed by many to be running for governor in Ohio next year.