Graham: I'm seeking to make Trump successful 'but not at all costs'

Sen. Lindsey GrahamLindsey Olin GrahamImpeachment week: Trump probe hits crucial point Graham on the impeachment inquiry: 'I made my mind up. There's nothing there' Rand Paul says Trump has 'every right' to withhold Ukraine aid over corruption MORE (R-S.C.) says he chose to be "reflective" after losing to President TrumpDonald John TrumpThis week: House kicks off public phase of impeachment inquiry Impeachment week: Trump probe hits crucial point Judd Gregg: The big, big and bigger problem MORE in the 2016 Republican primary race.

The longtime Senator appears in a promo video for the next episode of "Axios on HBO."

"[Hillary ClintonHillary Diane Rodham Clinton3 ways government can help clean up Twitter Intelligence Democrat: Stop using 'quid pro quo' to describe Trump allegations The Memo: Bloomberg's 2020 moves draw ire from Democrats MORE] was secretary of State, first lady, United States senator. She lost to Donald Trump," Graham tells Axios in the promo."

"I lost to Donald Trump," he added.

Graham also tells the news outlet that he chose "to try to find out how to make Trump successful but not at all costs."

Throughout Trump's presidency, Graham has been one of the president's staunchest supporters.

However, Graham — a known defense hawk — was one of Trump's loudest critics after the president decided to remove U.S. troops from the northeastern border of Syria last week.

At the time, Graham said the policy move could end up being the biggest mistake of Trump's presidency if it isn't reversed.

Similarly, the senator, a member of the Senate Foreign Relations Committee, showed apprehension over the Turkish cease-fire that was facilitated by Vice President Pence and Secretary of State Mike PompeoMichael (Mike) Richard PompeoIran lays foundation for second nuclear plant: report Pompeo knocks Iran's treatment of UN nuclear inspector Reagan statue unveiled near site where he called for Gorbachev to 'tear down' Berlin Wall MORE earlier this week. 

General Mazloum Abdi, the commander of the Syrian Democratic Forces, "is concerned about the cease-fire holding and was emphatic that he will never agree to the ethnic cleansing of Kurds that is being proposed in Ankara," Graham tweeted.

"A buffer zone is acceptable to the Kurds but a military occupation that displaces hundreds of thousands is not a safe zone. It is ethnic cleansing," he added.

The cease-fire is supposed to last five days, during which Kurdish forces will vacate Turkish President Recep Tayyip Erdoğan's desired "safe zone."