Donald Trump's continued threats to obstruct investigations into his campaign's collusion with Russia could be his undoing. And that's according to a Republican senator.

Donald Trump’s presidency is in serious trouble, and every day he is making it worse for himself.

In his increasingly desperate attempts to shut down the investigation into his campaign’s collusion with Russia, Trump has hinted at firing special counsel Robert Mueller and is making it plainly obvious that he wants his attorney general, Jeff Sessions, to resign so that Trump can appoint an even more loyal crony in his place — one willing to violate any laws or ethical obligations to assist in Trump’s coverup.

If Trump follows through on any of those threats, it just might be the nail in the coffin of Trump’s brief and already failing presidency, according to Republican Sen. Lindsey Graham.

GRAHAM: If Jeff Sessions is fired, there will be holy hell to pay. Any effort to go after Mueller could be the beginning of the end of the Trump presidency, unless Mueller did something wrong. Right now, I have no reason to believe that Mueller is compromised. If you’ve got reason to believe he is compromised and shouldn’t be serving as special counsel, let me know. I’m working on legislation that I want to introduce next week, with Republicans and some Democrats — I think you’ve got all the Democrats, I hope we get a good number of Republicans — that will say the following: “A special counsel cannot be fired when they were empaneled to investigate the president and his team, unless you have judicial review of the firing.” Not just for Trump but for any future president. We need a check and balance here..

Graham was a harsh critic of Trump during the 2016 campaign. However, like most of his party, he has been in lockstep with Trump when it comes to voting on Trump’s nominees and his agenda. In fact, when it comes to holding Trump accountable, his party has done very little indeed, at best offering vague condemnations without taking any action.

Trump’s war on Sessions, however, has raised the ire of Senate Republicans who like Sessions far more than they like Trump and who do not appreciate attacks on their former colleague. Graham has been one of the harsher critics of such attacks, and even told CNN that “if Jeff Sessions is fired, there will be holy hell to pay.”

There might also be “holy hell” for firing Mueller. With every act of desperation, Trump is only making himself appear more guilty. As Nick Ackerman, one of the Watergate prosecutors, said earlier this week, “Everything this president has done cries out guilt.”

He already fired FBI Director James Comey for refusing to shut down the investigation, and by all accounts, he seems eager to get rid of the special counsel. And Sessions. And anyone else who is unwilling to protect Trump and his closest friends and family from the mounting evidence that they conspired with Russia to install Trump in the White House.

Trump still seems to believe he can bluster, bully, and tweet his way out of his mounting troubles. But at his current rate of obstruction, he’s going to find himself out of the White House instead.