On Monday in South Carolina, Sen. Lindsey Graham (R-S.C.) joined the widening field of Republicans running for president.

Graham has been a senator since 2002 after serving as a congressman for eight years. He is known for his almost moderate stances on domestic affairs -- namely, immigration and climate change -- but for being hawkish when it comes to the military and defense. The senator is a former Air Force judge and lawyer, who bills himself as an expert on international affairs and has made multiple trips to Iraq and Afghanistan.

Graham's announcement speech hinged on foreign policy: He argues that President Obama has made the country less safe, and he is running for president because he fears the world is "falling apart."

Learn where Sen. Graham stands on five issues Millennials care about: immigration, LGBT rights, the environment, marijuana, and higher education.

1. College costs and student debt.

Sen. Graham is known for his "pro-lender" stance when it comes to student loans and student loan debt, according to a Credible report published by the Huffington Post. From Credible:

"In 2005, Senator Graham voted against an education funding amendment sponsored by Senator Edward Kennedy and co-sponsored by then Senators Barack Obama and John Kerry, among others. The amendment, which passed, closed $11 billion in corporate tax loopholes and used the money to restore vocational education programs that had been cut, to increase Pell Grants to $4,500, and to increase student loan forgiveness for science and math teachers to $23,000."

Graham also voted against two other measures regarding student loans and student debt. In 2010, he opposed a law that strengthened Pell Grants and cut subsidies for private student loan lenders. He also voted against Sen. Warren's amendment to allow student borrowers to refinance at a 3.9 percent interest rate, paid for by tax increases on wealthy Americans.

2. Marijuana

Sen. Graham has not been vocal on the topic of marijuana, but what he has said (or at least what his office has written) is interesting, if not slightly contradictory.

Graham has said he opposes legalization of recreational marijuana, but he seems to support medical marijuana.

"I'm against legalizing marijuana for recreational purposes," Graham stated in 2014, according to WBTV. "But when it comes to medicinal marijuana and this oil, I think politicians should embrace what makes sense. When it comes to issues like this, I don't want to be academic in thought. This is about people. This is about families with sick children. Why should someone in my position get in the way of helping a child, if you can reasonably and logically do it?"

Graham is referring to therapeutic CBD from a strain known as "Charlotte's Web." This strain has been bred to be low in THC and high in CBD. It is given in liquid form to children suffering from pediatric epilepsy.

Despite this, Graham has said he opposed the Obama administration's decision not to prosecute medical marijuana users:

“Attorney General Eric Holder has announced that the Justice Department will not prosecute purveyors of medical marijuana provided they are in compliance with state and local laws. I do not support this policy, as I feel it is tantamount to federal legalization of medical marijuana and creates an inconsistent federal enforcement policy between states,” Graham said in a letter to a constituent. (h/t to Republicans Against Marijuana Prohibition.)

3. Immigration

Sen. Graham is far more moderate on the topic of immigration than his fellow Republicans. Along with another presidential candidate, Sen. Marco Rubio (R-Fl.), Graham was part of the "gang of eight" -- eight lawmakers who worked together across party lines in 2013 on a bipartisan immigration reform bill. The bill passed the Senate but ultimately died in the Republican-controlled House of Representatives.

Regardless, immigration will be a key topic for this election, and Graham believes that his party wrong on this issue.

“If we keep playing this game that self-deportation is the only answer for the Republican Party, we will have destroyed our chances in 2016 and dealt a death blow to our party because by 2050 the majority of the country is going to be African American, Hispanic, and Asian,” Graham stated in 2014 on CBS’s “Face the Nation.”

Graham also believes in a pathway to citizenship.

"If I were president of the United States, I would veto any bill that did not have a pathway to citizenship," Graham said last month to USA Today. "You would have a long, hard path to citizenship ... but I want to create that path because I don't like the idea of millions of people living in America for the rest of their lives being the hired help. That's not who we are."

Back in 2014, he laid out a plan on "Face the Nation": “A pathway to citizenship, after you secure the border, control who gets a job, more legal immigrations where they have to pass a criminal background check, learn the English language, wait 10 years before you can apply for a green card."

4. Climate Change.

Sen. Lindsey Graham also departs from his party on the topic of the environment and global warming.

The majority of the time, Graham accepts that climate change exists and is man-made. In 2009, he co-authored a New York Times op-ed with then-Sen. John Kerry (D-Mass.) on the subject.

"First, we agree that climate change is real and threatens our economy and national security," the op-ed read. "That is why we are advocating aggressive reductions in our emissions of the carbon gases that cause climate change. We will minimize the impact on major emitters through a market-based system that will provide both flexibility and time for big polluters to come into compliance without hindering global competitiveness or driving more jobs overseas."

And though Graham has wavered on the topic -- voting against the climate bill he co-authored in 2010 and seemingly bowing to the opinion that climate change is not real, saying the "science has changed."

In March 2015, at a talk with the Council on Foreign Relations, Graham was asked again about climate change. He response is confusing to say the least, but he appears to be arguing that although climate change is real, we cannot afford solutions that will kill jobs:

"I did the trifecta. I said that it's real, that man has contributed to it in a substantial way. But the problem is Al Gore's turned this thing into religion. You know, climate change is not a religious problem for me, it's an economic, it is an environmental problem.

"So I think the Republican Party has to do some soul-searching. Before we can be bipartisan, we've got to figure out where we are as a party. What is the environmental platform of the Republican Party? I don't know, either.

"So I'd like to come up with one. I'd like to have a debate within the party. Can you say that climate change is a scientifically sound phenomenon? But can you reject the idea you have to destroy the economy to solve the problem, is sort of where I'll be taking this debate."

Here is a video of his response:

5. LGBT Rights

In terms of LGBT rights, Graham looks like the rest of his party. He voted in favor of a constitutional amendment to ban same sex marriage in 2006. He has a 100 percent rating from the Christian Coalition of America, according to his Senate campaign site.