It is extremely illegal to use party identification as a basis for hiring or firing civil service employees.
I'm not sure there is even a way for them to know an employees party identification. So if they start firing people, they will be firing a lot of Republicans as well as Democrats. If they found a way to fire only Democrats, they'd be sure to be hit with a massive class action lawsuit which the government would definitely lose, exposing them to paying out even more money.
Moron Cruz appears to believe only Democrats work for the EPA, IRS and USDOL. As someone who worked for both DOL & IRS, I can assure Cruz there are plenty of Republicans working at both agencies. It's disgusting these agencies are being portrayed as "Democrat". These agencies are some of the most important agencies in the government for protecting the population (and the IRS is essential to fund the government - you know even the Department of Defense and ICE can't operate without taxes collected by the IRS).