Sen. Lindsey Graham (R-S.C.) ended his long-shot presidential bid Monday, telling supporters in a web video that he succeeded in changing the conversation about how to fight the Islamic State.

"Four months ago, at the very first debate, I said that any candidate who did not understand that we need more American troops on the ground in Iraq and Syria to defeat ISIL was not ready to be commander in chief," said Graham. "At that time, no one stepped forward to join me. Today, most of my fellow candidates have come to recognize this is what's needed." The Islamic State, a terrorist organization that controls large tracts of Iraq and Syria, is also known as ISIS and ISIL.

Sen. Lindsey Graham (R-S.C.) announced he is suspending his presidential campaign in this video released on Dec. 21. (Youtube/Senator Lindsey Graham)

Graham's bid, which never cracked 1 percent in primary polls, locked up an unusual amount of elite support. Sen. John McCain (R-Ariz.), his closest friend in the Senate, immediately endorsed Graham and campaigned with him throughout New Hampshire. Scores of South Carolina donors, who might have otherwise jumped to higher-polling candidates, stayed on Graham's team out of loyalty -- and on the chance that his moderate campaign broke through.

"I think we all owe him a debt of gratitude," said David Wilkins, the South Carolina chairman of Graham's finance committee, who served as ambassador to Canada under George W. Bush. "His decision frees up a lot of very strong Lindsey Graham supporters here to make new endorsements, but it's too soon for me. This is Lindsey's day."

By leaving the race Monday, Graham was able to remove his name from his home state's primary ballot, creating the sort of free-for-all in the first Southern contest that candidates such as Jeb Bush and Sen. Marco Rubio (R-Fla.) have desired for months. Matt Moore, the chairman of the South Carolina Republican Party, confirmed that Graham was off the ballot within 40 minutes of the announcement.

That spared Graham a likely defeat in his home state, and marked the end of a candidacy that even opponents came to respect. Graham liked to tell audiences that he had been dubbed "Lindsey Gomez" and "Grahamnesty" for his work on multiple immigration reform bills, yet won a competitive 2014 Senate re-nomination fight. He hoped that proved the GOP was more moderate than advertised; his political opponents credited his success to his jovial, honest, and open personality.

"To his credit, I think Lindsey Graham is one of the few who has been at least honest about suggesting 'here is something I would do that the president is not doing,'" President Obama told NPR in an interview published shortly before Graham quit the race. "He doesn't just talk about being louder or sounding tougher in the process."

Just six days ago, Graham -- whose sizable Senate campaign war chest gave him more financial stability than other underdogs -- was resisting any rumor that he might quit or pull his name off the ballot. In the Las Vegas debate spin room, after what will have been his last "undercard" performance, Graham said that he would push at least through the New Hampshire primary. Yet privately, according to Graham strategist Brett O'Donnell, the senator was thinking about a way out of the race.

"It’s something he’s been contemplating for a while and he waited for a bit, just wanted to make sure," O'Donnell said in an interview. "It came together over the weekend but it’s been on his mind for a few weeks. If you know him, you know he’s fiscally responsible. He was raised that way and he didn’t want to go into debt on the campaign. I know that was weighing on him. He wanted to go out on his own terms. So, after a great debate last week -- he dominated the undercard in our view -- it was time. He ends it on a high."

Still, he would have preferred to end it a little higher. In January, when Graham announced his presidential exploratory committee, he was excited about the chance to challenge Sen. Rand Paul (R-Ky.) to a debate over his "isolationism." When Sen. Ted Cruz (R-Tex.) began to rise in polls, Graham condemned his politics, warning a gathering of the Republican Jewish Coalition that unbending right-wing stances would doom the party in 2016.

"If you are going to tell a woman who has been raped she has to carry the child of a rapist, you’re losing most Americans," said Graham. "Good luck with that.”

At a forum hosted by the Republican Jewish Coalition, Republican presidential candidate Sen. Lindsey Graham (S.C.) offered critiques for the GOP, specifically calling out rival Donald Trump's stance on immigration and the views of Sen. Ted Cruz (Tex.) on abortion. (Republican Jewish Coalition)

Yet it was Donald Trump, the Republican frontrunner whom no one saw coming, that absorbed most of Graham's attacks. The senator, a retired colonel in the Air Force Reserves and a sponsor of multiple immigration reform bills, characterized Trump as a "xenophobic" ignoramus whose campaign was making the country and Republican Party weaker.

"Donald Trump has done the one single thing you cannot do: Declare war on Islam itself," Graham said at the final undercard debate. "ISIL would be dancing in the streets; they just don't believe in dancing."

Network and party decisions to cleave the swollen Republican field into main stage and "undercard" debates meant that Graham never got to confront Paul, Cruz, or Trump. An effort to change the format, which O'Donnell participated in, did not elevate the candidate to prime time. He was left making his arguments on the more accessible, and familiar, format of cable news interviews. On Monday, he returned to that role, giving CNN an interview about how the Republican Party needed to follow his lead on foreign policy.

While Republican Donald Trump's presidential campaign is still alive and kicking, these four candidates have two things in common: they all attacked Trump and they all later left the 2016 presidential race. (Sarah Parnass/The Washington Post)

"My campaign has come to the point where I need to think about getting out and helping somebody else," Graham told CNN's Kate Bolduan after the announcement. "Jeb and Marco are very sync with where I’m at. [So are] Christie and Kasich."

Graham's actual endorsement might be in less demand than those of his donors -- or McCain. But by bowing out, Graham will not face voters again until 2020, after the next president's full first term.

"I want to help whoever's president," Graham told reporters in Las Vegas. "I don't care if it's Donald Trump or Hillary Clinton. We've got a war we need to win."