This post has been updated to note that Graham has now officially gotten into the race for president.
South Carolina Sen. Lindsey Graham officially announced that he is getting into the presidential race Monday morning in Central, S.C., the small upstate town where he was raised. Graham, 59, is the senior senator from South Carolina and one of the few in the crowded Republican primary field with military experience. He says he's running for president because "the world is falling apart."
Graham is also one of the Senate's leading Republican voices on foreign policy and has been a fierce critic of President Obama on the topic. In interviews leading up to his announcement, he has indicated that his eventual campaign would emphasize that expertise and his views on fighting national security threats including the self-proclaimed Islamic State.
Here are five things you should know:
1. Both of Graham's parents died, within 15 months of each other, when he was in college
When Graham was a student at the University of South Carolina, both his parents died. His mother, Millie Graham, died at age 52 of Hodgkin lymphoma. She was soon followed by his father, F.J. — known in his hometown of Central as "the Dude" — who died of a heart attack at age 69. Graham's only sister, Darline, was just 13 years old.
Friends say Graham was a devoted brother, returning home each weekend to be with his sister. He ultimately adopted her after enlisting in the Air Force so that she could receive his military benefits.
In an ad cut for his 2014 race, Graham's sister recounted how her older brother cared for her after their parents died.
"It was hard when we lost my mom and dad," Darline Graham Nordone said. "Lindsey assured me that he was going to take care of me, and he was going to be there for me. That's just who he is."
2. He catapulted onto the national stage because of his role in the Clinton impeachment proceedings
Graham got his start in politics in the South Carolina Legislature in 1992 before winning an open U.S. House seat in 1994, campaigning on his conservative record. He was part of the failed 1997 push to oust then-House Speaker Newt Gingrich. But it was his role in the House impeachment and Senate trial of President Bill Clinton that put him on the map.
"Is this Watergate or Peyton Place?" Graham notably asked fellow lawmakers on the House Judiciary Committee in October 1998 as the committee moved toward a formal impeachment inquiry by Congress against then-President Clinton.
While Republicans lost that case and the Senate later acquitted Clinton, the impeachment process catapulted Graham onto the national stage. His role became a staple of his campaign stump speeches soon after and he was immediately a darling of cable news channels fascinated by the ordeal.
3. Graham recently retired from the Air Force Reserve
Graham, one of the few Republicans in the 2016 field who have served in the military, announced last week that he would retire from the Air Force Reserve. The 59-year-old is one year shy of the U.S. Air Force's mandatory retirement age of 60.
His military career spans three decades. He was awarded the Bronze Star in 2014 for meritorious service for his role as a senior legal adviser to the Air Force during combat operations in Afghanistan from August 2009 to July 2014. He spent 6 1/2 years on active duty in the Air Force and later served in the South Carolina Air Guard. Graham transferred to the Air Force Reserve in 1995 and remained with the reserve through his career in the Senate, which started in 2003.
"It's been one of the great honors of my life to serve in the Air Force in some capacity for more than three decades," Graham said in a statement. "The Air Force has been one of the best things that has ever happened to me. It identified and developed my talent, and helped me become useful to my country. It offered me adventure and showed me the world. It gave me a purpose bigger than myself. It put me in the company of patriots. It's been almost like family to me. I'm going to miss it an awful lot, and I wouldn't leave if they weren't making me."
His retirement is effective June 1, the same day that he announced his candidacy for president.
4. While he's a constant Obama agitator, he has a record of reaching across the aisle
Make no mistake: Graham is a Republican through and through. But he's also well-known in the Senate for reaching across the aisle to work with Democrats on issues — most notably on immigration.
In a recent visit to Iowa, he said that Republicans in Congress should join forces with Democrats on immigration reform to find a "practical solution." Unlike virtually any other candidate in the Republican field, he supports letting some immigrants living in the United States illegally stay if they meet certain conditions. He was a member of the "Gang of Eight" bipartisan senators in the White House who wrote legislation that would eventually offer citizenship for those immigrants. The legislation passed the Senate in 2013 but died in the more conservative House.
His willingness to reach across the aisle was a liability in Graham's re-election race last year, but so far he is brandishing it as a selling point in the GOP presidential primary.
"The reason I had six primary opponents in my last election is because I've been accused of working with Democrats too much," he said on CBS This Morning in May. "In my view, Democrats and Republicans work together too little. And I would try to change that if I got to be president."
5. He has never sent an email
Earlier this year, Graham made headlines when he quipped that he had "never sent" an email, despite 12 years as a U.S. senator and eight as a representative before that. The comment, which quickly went viral, came in response to a question by NBC's Chuck Todd in a discussion about Hillary Clinton's use of a home-based email server while serving as secretary of state.
Asked if he had a private email account, Graham told Todd: "I don't email. No, you can have every email I've ever sent. I've never sent one."
Graham does, however, regularly carry a cellphone. But don't expect him to wade into the iPhone vs. Android debate anytime soon. His device of choice is a flip phone.