Lindsey Graham: 5 things to know about the South Carolina Senator

The former Air Force Colonel served for more than 33 years

South Carolina Senator Lindsey Graham announced his bid for the Republican presidential nomination on Monday.

“I have more national security experience than any other candidates in this race,” he said to supporters. "I'm ready. I want to be president to defeat the enemies that are trying to kill us."

The three-term Senator has said he knows his polling numbers are low, but he wants to influence debates on national security in which he has years of experience.

1. Mr Graham is outspoken against same-sex marriage.

The three-term Senator believes marriage equality promotes polygamy and marriage can only be between a man and a woman.

"If the Supreme Court rules that same-sex marriage bans are unconstitutional — that it violates the Constitution to try to limit marriage between a man and a woman, that's clearly the law of the land unless there's a constitutional amendment to change it — what legal rationale would be in play that would prohibit polygamy?" he once asked Loretta Lynch.

"What's the legal difference between a state ban on same-sex marriage being unconstitutional but a ban on polygamy being constitutional?"

2. He believes Republicans should side with Democrats on immigration.

"The reason I had six primary opponents in my last election is because I've been accused of working with Democrats too much," he told CBS. "In my view, Democrats and Republicans work together too little. And I would try to change that if I got to be president."

3. Mr Graham has an extensive military background.

He served with the Air Force for more than 33 years and told the Daily Caller that while his experience is a major asset the US president need not have served in the military.

“You get to walk in the shoes of the people who you’re going to be in charge of. So that’s all good," he said. "It doesn’t mean you have to be in the military to be a good commander-in-chief. But I think having that experience is a positive.”

4. He has never sent an email.

Despite working 12 years as a US senator and 8 years as a representative, Mr Graham told NBC that he's never sent mail on the interwebs.

"I don't email. No, you can have every email I've ever sent. I've never sent one."

5. Mr Graham's parents passed away while he attended college.

While attending the University of South Carolina, his parents passed away within 15 months of each other. Mr Graham was forced to raise his sister Darline who was only 13 years old.