WATCH: Top GOP senator warns firing Mueller and Sessions would be 'beginning of the end' of Trump

Sen. Lindsey Graham (R-SC) on Thursday drew a bright red line for President Donald Trump when it comes to any decision he makes to fire Attorney General Jeff Sessions or special counselor Robert Mueller.

Speaking with CNN's Manu Raju, Graham said there would be "holy hell" to pay if Trump fired his embattled attorney general, while suggesting the consequences for the president could be even more dire if he went through with firing Mueller.

"If Jeff Sessions is fired, there will be holy hell to pay," Graham stated bluntly. "Any effort to go after Mueller could be the beginning of the end of the Trump presidency, unless Mueller did something wrong."

Graham also said he was working on bipartisan legislation stating that a special prosecutor who is investigating the president cannot be fired by the president without "judicial review of the firing."

"We need a check and balance here," Graham explained. "The law is above any presidential red line."

Watch the whole interview below.